Other Comprehensive (Loss) Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Before-Tax Amount
Other Comprehensive Income (Loss), before Tax	$ 103.6	$ (120.6)	$ 8.1
Income Tax (Expense) Benefit
Other Comprehensive Income (Loss), Tax	(39.2)	45.2	(2.8)
Net-of-Tax Amount
Other comprehensive income (loss), net of tax	64.4	(75.4)	5.3
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Before-Tax Amount
Other Comprehensive Income (Loss), before Reclassifications, before Tax	(6.1)	(129.5)	2.2
Other Comprehensive Income (Loss), before Tax	104.6	(120.7)	7.9
Income Tax (Expense) Benefit
Other Comprehensive Income (Loss) before Reclassifications, Tax	2.3	48.3	(0.7)
Other Comprehensive Income (Loss), Tax	(39.5)	45.1	(2.8)
Net-of-Tax Amount
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(3.8)	(81.2)	1.5
Other comprehensive income (loss), net of tax	65.1	(75.6)	5.1
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Before-Tax Amount
Other Comprehensive Income (Loss), before Reclassifications, before Tax	(12.9)	(39.0)	87.0
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	1.1	(1.8)	1.5
Income Tax (Expense) Benefit
Other Comprehensive Income (Loss) before Reclassifications, Tax	4.9	14.5	(32.5)
Reclassification from AOCI, Current Period, Tax	(0.4)	0.7	(0.5)
Net-of-Tax Amount
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(8.0)	(24.5)	54.5
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0.7	(1.1)	1.0
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Before-Tax Amount
Other Comprehensive Income (Loss), before Reclassifications, before Tax	6.8	(90.5)	(84.8)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	3.0	10.6	4.2
Income Tax (Expense) Benefit
Other Comprehensive Income (Loss) before Reclassifications, Tax	(2.6)	33.8	31.8
Reclassification from AOCI, Current Period, Tax	(1.2)	(3.9)	(1.6)
Net-of-Tax Amount
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	4.2	(56.7)	(53.0)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	1.8	6.7	2.6
Accumulated Defined Benefit Plans Adjustment, Removal Of Obligation Attributable to Parent [Member]
Before-Tax Amount
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	106.6
Income Tax (Expense) Benefit
Reclassification from AOCI, Current Period, Tax	(40.2)
Net-of-Tax Amount
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	66.4
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Before-Tax Amount
Other Comprehensive Income (Loss), before Reclassifications, before Tax	(0.1)	(0.2)	1.0
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	(0.4)	(0.1)	(1.0)
Other Comprehensive Income (Loss), before Tax	(0.5)	(0.3)	0.0
Income Tax (Expense) Benefit
Other Comprehensive Income (Loss) before Reclassifications, Tax	0.0	0.1	(0.3)
Reclassification from AOCI, Current Period, Tax	0.2	0.0	0.3
Other Comprehensive Income (Loss), Tax	0.2	0.1	0.0
Net-of-Tax Amount
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(0.1)	(0.1)	0.7
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(0.2)	(0.1)	(0.7)
Other comprehensive income (loss), net of tax	(0.3)	(0.2)	0.0
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Before-Tax Amount
Other Comprehensive Income (Loss), before Tax	(0.3)
Income Tax (Expense) Benefit
Other Comprehensive Income (Loss), Tax	0.1
Net-of-Tax Amount
Other comprehensive income (loss), net of tax	(0.2)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Before-Tax Amount
Other Comprehensive Income (Loss), before Tax	(0.2)	0.4	0.2
Income Tax (Expense) Benefit
Other Comprehensive Income (Loss), Tax	0.0	0.0	0.0
Net-of-Tax Amount
Other comprehensive income (loss), net of tax	$ (0.2)	$ 0.4	$ 0.2