Annual report pursuant to Section 13 and 15(d)

Postretirement Benefits Benefit Obligations, Plan Assets and Funded Status (Details)

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Postretirement Benefits Benefit Obligations, Plan Assets and Funded Status (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Change in Plan Assets [Roll Forward]      
Fair Value of Plan Assets at Previous December 31 [1] $ 687.9    
Fair Value of Plan Assets at December 31 $ 546.1 [2] $ 687.9 [1]  
Funded Percentage [3] 76.1752% 74.65003%  
Pension Plans [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Assets for Plan Benefits, Defined Benefit Plan $ 3.5 $ 0.0  
Change in Benefit Obligations [Roll Forward]      
Benefit Obligation at Previous December 31 921.5 1,035.5  
Interest Cost 28.4 35.8 $ 47.9
Participant Contributions 0.0 0.0  
Actuarial (Gains) Losses 58.0 49.0  
Benefit Payments (56.6) (73.6)  
Settlement Payments (234.4) (125.2)  
Benefit Obligation at December 31 716.9 921.5 1,035.5
Change in Plan Assets [Roll Forward]      
Fair Value of Plan Assets at Previous December 31 687.9 736.4  
Actual Return on Plan Assets 75.5 75.7  
Employer Contributions 73.7 74.6  
Participant Contributions 0.0 0.0  
Benefit Payments (56.6) (73.6)  
Settlement Payments (234.4) (125.2)  
Fair Value of Plan Assets at December 31 546.1 687.9 736.4
Funded Status at December 31 (170.8) (233.6)  
Amounts Recognized in Consolidated Balance Sheet [Abstract]      
Accrued Expenses 3.8 10.5  
Postretirement Benefit Liabilities 170.5 223.1  
Net Amount Recognized 174.3 233.6  
Other Postretirement Benefit Plans [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Assets for Plan Benefits, Defined Benefit Plan 0.0 0.0  
Change in Benefit Obligations [Roll Forward]      
Benefit Obligation at Previous December 31 40.6 43.5  
Interest Cost 1.2 1.4 1.8
Participant Contributions 0.5 0.5  
Actuarial (Gains) Losses 0.0 (0.9)  
Benefit Payments (3.6) (3.9)  
Settlement Payments 0.0 0.0  
Benefit Obligation at December 31 38.7 40.6 43.5
Change in Plan Assets [Roll Forward]      
Fair Value of Plan Assets at Previous December 31 0.0 0.0  
Actual Return on Plan Assets 0.0 0.0  
Employer Contributions 3.1 3.4  
Participant Contributions 0.5 0.5  
Benefit Payments (3.6) (3.9)  
Settlement Payments 0.0 0.0  
Fair Value of Plan Assets at December 31 0.0 0.0 $ 0.0
Funded Status at December 31 (38.7) (40.6)  
Amounts Recognized in Consolidated Balance Sheet [Abstract]      
Accrued Expenses 3.7 4.1  
Postretirement Benefit Liabilities 35.0 36.5  
Net Amount Recognized 38.7 40.6  
Nonqualified Plan [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Pension Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation $ 33.2 $ 34.5  
[1] (A)See Note 7 – Fair Value Measurements for a description of levels within the fair value hierarchy. The level in the fair value hierarchy within which the fair value measurement is classified is determined based on the lowest level input that is significant to the fair value measurement in its entirety. A description of the valuation methodologies is provided following these tables. There were no transfers in and/or out of Level 1 and Level 2 in 2016.
[2] (A)See Note 7 – Fair Value Measurements for a description of levels within the fair value hierarchy. The level in the fair value hierarchy within which the fair value measurement is classified is determined based on the lowest level input that is significant to the fair value measurement in its entirety. A description of the valuation methodologies is provided following these tables. There were no transfers in and/or out of Level 1 and Level 2 in 2017.
[3] (A) As all of the Company's plans are frozen, the projected benefit obligation and the accumulated benefit obligation are equal. As of December 31, 2017 and 2016, the projected and accumulated benefit obligations for all of the Company's pension plans were in excess of plan assets.