Annual report pursuant to Section 13 and 15(d)

Postretirement Benefits Pretax Activity in Accumulated Other Comprehensive Income (Loss) (Details)

v3.3.1.900
Postretirement Benefits Pretax Activity in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Net Actuarial Losses [Abstract]    
Percentage of benefit obligation or market value of assets, over which actuarial gains and losses are subject to amortization (in hundredths) 10.00%  
Pension Plans [Member]    
Prior Service Costs (Credits) [Abstract]    
Beginning balance $ 0.0 $ 0.0
Prior service credits arising during the period 0.0 0.0
Amount recognized as component of net benefit costs 0.0 0.0
Ending balance 0.0 0.0
Net Actuarial Losses [Abstract]    
Beginning balance 528.6 441.3
Actuarial (gains) losses arising during the period 31.0 130.2
Amount recognized as component of net benefit costs (101.8) (42.9)
Ending balance 457.8 528.6
Total 457.8 528.6
Estimated pretax net actuarial loss in accumulated other comprehensive income (loss) expected to be recognized over the next year 17.4  
Other Postretirement Benefit Plans [Member]    
Prior Service Costs (Credits) [Abstract]    
Beginning balance (11.6) (12.5)
Prior service credits arising during the period 0.0 0.0
Amount recognized as component of net benefit costs 0.7 0.9
Ending balance (10.9) (11.6)
Net Actuarial Losses [Abstract]    
Beginning balance 7.3 2.3
Actuarial (gains) losses arising during the period (4.1) 5.0
Amount recognized as component of net benefit costs (1.3) 0.0
Ending balance 1.9 7.3
Total (9.0) $ (4.3)
Estimated pretax prior service (cost) credit in accumulated other comprehensive income (loss) expected to be recognized over the next year 0.7  
Estimated pretax net actuarial loss in accumulated other comprehensive income (loss) expected to be recognized over the next year $ 0.0