Income Tax (details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Components of Deferred Tax Assets and Liabilities [Abstract]
Current deferred tax assets	$ 57.1	$ 52.2
Current deferred tax liabilities	3.3	0.8
Net current deferred tax asset	53.8	51.4
Non-current deferred tax assets	192.0	55.7
Non-current deferred tax liabilities	7.2	5.0
Net non-current deferred tax asset	184.8	50.7
Total deferred tax asset	238.6	102.1
Deferred Tax Assets, Tax Deferred Expense [Abstract]
Long-term contracts	234.6	85.0
Post-retirement benefits other than pensions	28.6	31.8
Pension and other employee benefit plans	(3.9)	(19.5)
Employee compensation accruals	35.9	30.7
Depreciation and amortization	(106.9)	(86.3)
Inventory	(1.4)	(0.5)
Interest swap contracts	(0.1)	1.8
State income tax credits	49.8	42.9
Accruals and reserves	20.2	17.1
Deferred Tax Assets Deferred Production	19.5	(3.2)
Deferred Gain Severe Weather Event	(39.1)
Net operating loss carryforward	10.7	11.4
Other	1.1	(0.9)
Net deferred tax asset	249.0	110.3
Valuation allowance	(10.4)	(8.2)
Net deferred tax asset	238.6	102.1
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]
Tax at U.S. Federal statutory rate	4.0	98.1	104.2
State income taxes, net of Federal benefit	(11.6)	0.9	(4.6)
Foreign rate differences	(4.6)	1.4	(4.3)
Research and Experimentation Credit	3.2	10.2	(10.3)
Domestic Production Activities Deduction	8.8	4.7	(4.0)
Interest on assessments	0.3	0.8	(1.2)
Other	(0.2)	0.6	(1.6)
Total provision for income taxes	(24.1)	86.9	78.2
Current Income Tax Expense (Benefit) [Abstract]
Federal	89.8	59.6	28.4
State	1.9	3.4	1.1
Foreign	4.3	5.8	0.6
Total current	96.0	68.8	30.1
Deferred Income Tax Expense (Benefit) [Abstract]
Federal	(104.0)	20.3	54.3
State	(19.0)	(2.0)	(8.2)
Foreign	2.9	(0.2)	2.0
Total Deferred	(120.1)	18.1	48.1
Total provision for income taxes	(24.1)	86.9	78.2
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning Balance	15.5	15.2	23.2
Gross increases related to current period tax positions	4.2	6.1	9.4
Gross increases related to prior period tax positions	1.8	33.5
Gross decreases related to prior period tax positions	(3.8)	(9.3)	(16.2)
Statute of limitations' expiration	(0.8)	(0.8)	(1.2)
Settlements		(29.2)
Ending Balance	16.9	15.5	15.2
Summary Pretax Income [Abstract]
U.S.	(33.6)	265.9	276.8
International	45.0	14.4	21.0
Total	$ 11.4	$ 280.3	$ 297.8