| 
           Fair Value Measurements (Details) (Fair Value, Measurements, Recurring [Member], USD $) 
        In Millions, unless otherwise specified  | 
        
           Dec. 31, 2014 
         | 
        
           Dec. 31, 2013 
         | 
      
|---|---|---|
| Assets: | ||
| Cash equivalents | $ 257.5bc_FairValueAssetsMeasuredOnRecurringBasisCashEquivalents | $ 179.4bc_FairValueAssetsMeasuredOnRecurringBasisCashEquivalents | 
| Short-term investments in marketable securities | 83.2bc_ShortTermInvestmentsInMarketableSecuritiesFairValueDisclosure | 12.7bc_ShortTermInvestmentsInMarketableSecuritiesFairValueDisclosure | 
| Restricted cash | 15.6bc_FairValueAssetsMeasuredOnRecurringBasisRestrictedCash | 6.5bc_FairValueAssetsMeasuredOnRecurringBasisRestrictedCash | 
| Derivatives | 11.1us-gaap_DerivativeAssets | 2.6us-gaap_DerivativeAssets | 
| Total assets | 367.4us-gaap_AssetsFairValueDisclosure | 201.2us-gaap_AssetsFairValueDisclosure | 
| Liabilities: | ||
| Derivatives | 3.6us-gaap_DerivativeLiabilities | 4.4us-gaap_DerivativeLiabilities | 
| Other | 52.8us-gaap_OtherLiabilitiesFairValueDisclosure | 51.0us-gaap_OtherLiabilitiesFairValueDisclosure | 
| Total liabilities | 56.4us-gaap_LiabilitiesFairValueDisclosure | 55.4us-gaap_LiabilitiesFairValueDisclosure | 
| Fair Value, Inputs, Level 1 [Member] | ||
| Assets: | ||
| Cash equivalents | 
130.7bc_FairValueAssetsMeasuredOnRecurringBasisCashEquivalents / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
        
119.7bc_FairValueAssetsMeasuredOnRecurringBasisCashEquivalents / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
      
| Short-term investments in marketable securities | 
9.7bc_ShortTermInvestmentsInMarketableSecuritiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
        
0.8bc_ShortTermInvestmentsInMarketableSecuritiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
      
| Restricted cash | 
15.6bc_FairValueAssetsMeasuredOnRecurringBasisRestrictedCash / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
        
6.5bc_FairValueAssetsMeasuredOnRecurringBasisRestrictedCash / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
      
| Derivatives | 
0us-gaap_DerivativeAssets / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
        
0us-gaap_DerivativeAssets / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
      
| Total assets | 
156.0us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
        
127.0us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
      
| Liabilities: | ||
| Derivatives | 
0us-gaap_DerivativeLiabilities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
        
0us-gaap_DerivativeLiabilities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
      
| Other | 
4.0us-gaap_OtherLiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
        
4.4us-gaap_OtherLiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
      
| Total liabilities | 
4.0us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
        
4.4us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
      
| Fair Value, Inputs, Level 2 [Member] | ||
| Assets: | ||
| Cash equivalents | 
126.8bc_FairValueAssetsMeasuredOnRecurringBasisCashEquivalents / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
        
59.7bc_FairValueAssetsMeasuredOnRecurringBasisCashEquivalents / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
      
| Short-term investments in marketable securities | 
73.5bc_ShortTermInvestmentsInMarketableSecuritiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
        
11.9bc_ShortTermInvestmentsInMarketableSecuritiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
      
| Restricted cash | 
0bc_FairValueAssetsMeasuredOnRecurringBasisRestrictedCash / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
        
0bc_FairValueAssetsMeasuredOnRecurringBasisRestrictedCash / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
      
| Derivatives | 
11.1us-gaap_DerivativeAssets / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
        
2.6us-gaap_DerivativeAssets / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
      
| Total assets | 
211.4us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
        
74.2us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
      
| Liabilities: | ||
| Derivatives | 
3.6us-gaap_DerivativeLiabilities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
        
4.4us-gaap_DerivativeLiabilities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
      
| Other | 
48.8us-gaap_OtherLiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
        
46.6us-gaap_OtherLiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
      
| Total liabilities | 
52.4us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
        
51.0us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
      
| Fair Value, Inputs, Level 3 [Member] | ||
| Assets: | ||
| Cash equivalents | 
0bc_FairValueAssetsMeasuredOnRecurringBasisCashEquivalents / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
        
0bc_FairValueAssetsMeasuredOnRecurringBasisCashEquivalents / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
      
| Short-term investments in marketable securities | 
0bc_ShortTermInvestmentsInMarketableSecuritiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
        
0bc_ShortTermInvestmentsInMarketableSecuritiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
      
| Restricted cash | 
0bc_FairValueAssetsMeasuredOnRecurringBasisRestrictedCash / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
        
0bc_FairValueAssetsMeasuredOnRecurringBasisRestrictedCash / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
      
| Derivatives | 
0us-gaap_DerivativeAssets / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
        
0us-gaap_DerivativeAssets / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
      
| Total assets | 
0us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
        
0us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
      
| Liabilities: | ||
| Derivatives | 
0us-gaap_DerivativeLiabilities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
        
0us-gaap_DerivativeLiabilities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
      
| Other | 
0us-gaap_OtherLiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
        
0us-gaap_OtherLiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
      
| Total liabilities | 
$ 0us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
        
$ 0us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember  | 
      
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- Definition 
          This element represents a certain statement of financial position asset caption which represents a class of assets, or which may include an individual asset, measured at fair value on a recurring basis. No definition available. 
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- Definition 
          This element represents restricted cash, which represents a class of assets, or which may include an individual asset, measured at fair value on a recurring basis. No definition available. 
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- Definition 
          This element represents the fair value disclosure for Short-term investments in marketable securities which are considered available-for-sale. No definition available. 
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- Definition 
          Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          Fair value of financial and nonfinancial obligations. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          Fair value portion of other liabilities. No definition available. 
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- Details 
          
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- Details 
          
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