Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Summary Pretax Income [Abstract]
U.S.	$ 739.4	$ 194.2	$ (499.8)
International	68.7	68.2	69.0
Income (loss) before income taxes and equity in net income of affiliates	808.1	262.4	(430.8)
Deferred Tax Liabilities, Net		(5.0)
Current
Federal	175.5	(91.0)	(17.1)
State	3.5	(0.9)	(2.1)
Foreign	5.5	4.0	4.2
Total current	184.5	(87.9)	(15.0)
Deferred
Federal	(119.1)	0.0	139.0
State	(48.9)	(2.0)	57.8
Foreign	4.1	(6.0)	9.3
Total Deferred	(163.9)	(8.0)	206.1
Total provision (benefit) for income taxes	20.6	(95.9)	191.1
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]
Tax at U.S. Federal statutory rate	283.3	91.8	(150.8)
State income taxes, net of Federal benefit	15.0	4.1	(12.2)
State income tax credits, net of Federal benefit	(4.1)	(9.0)	(7.7)
Foreign rate differences	(13.5)	(12.3)	(6.8)
Research and Experimentation	(3.3)	(3.0)	(10.9)
Domestic Production Activities Deduction	(17.8)	0.0	0.0
Interest on assessments	(1.0)	(3.7)	(0.6)
Valuation Allowance - U.S. Deferred Tax Asset	(241.9)	(167.2)	381.0
Other	3.9	3.4	(0.9)
Total provision (benefit) for income taxes	$ 20.6	$ (95.9)	$ 191.1
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
Tax at U.S. Federal statutory rate	35.00%	35.00%	35.00%
State income taxes, net of Federal benefit	1.90%	1.60%	2.80%
State income tax credits, net of Federal benefit	(0.50%)	(3.40%)	1.80%
Foreign rate differences	(1.70%)	(4.70%)	1.60%
Research and Experimentation	0.40%	1.10%	(2.50%)
Domestic Production Activities Deduction	(2.20%)	0.00%	0.00%
Interest on assessments	(0.10%)	(1.40%)	0.10%
Valuation Allowance - U.S. Deferred Tax Asset	(29.90%)	(63.70%)	(88.40%)
Other	0.50%	1.20%	0.20%
Total provision (benefit) for income taxes	2.60%	(36.50%)	(44.40%)
Deferred Tax Assets, Tax Deferred Expense [Abstract]
Long-term contracts	$ 142.4	$ 207.8
Post-retirement benefits other than pensions	27.2	29.2
Pension and other employee benefit plans	(64.4)	(48.8)
Employee compensation accruals	52.6	69.3
Depreciation and amortization	(124.6)	(120.4)
Inventory	2.1	2.9
Interest swap contracts	0.0	(1.0)
State income tax credits	70.5	70.5
Accruals and reserves	85.8	62.4
Deferred production	(2.4)	(3.3)
Deferred gain — severe weather event	(21.2)	(21.2)
Net operating loss carryforward	0.6	6.5
Other	(3.8)	(1.6)
Net deferred tax asset	164.8	252.3
Valuation allowance	(15.1)	(257.3)
Net deferred tax asset	149.7	(5.0)
Components of Deferred Tax Assets and Liabilities [Abstract]
Current deferred tax assets	0.0	53.2
Current deferred tax liabilities	0.0	(0.3)
Net current deferred tax asset	0.0	52.9
Non-current deferred tax assets	162.8	0.0
Non-current deferred tax liabilities	(13.1)	(57.9)
Net non-current deferred tax asset	149.7
Total deferred tax asset	149.7
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning Balance	5.9	18.4	$ 16.9
Gross increases related to current period tax positions	0.0	0.0	3.8
Gross increases related to prior period tax positions	0.3	0.9	0.4
Gross decreases related to prior period tax positions	0.0	(13.4)	(2.7)
Statute of limitations' expiration	0.0	0.0	0.0
Settlements	0.0	0.0	0.0
Ending Balance	6.2	$ 5.9	$ 18.4
State and Local Jurisdiction [Member]
Deferred Tax Assets, Tax Deferred Expense [Abstract]
Valuation allowance	(14.4)
Foreign Tax Authority [Member]
Deferred Tax Assets, Tax Deferred Expense [Abstract]
Valuation allowance	(0.7)
North Carolina [Member]
Deferred Tax Assets, Tax Deferred Expense [Abstract]
Valuation allowance	$ (12.8)