Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount	$ 10.2	$ 13.2	$ 15.0	$ 13.5
Summary Pretax Income [Abstract]
U.S.	552.4	655.0	426.6
International	110.7	101.2	108.0
Income before income taxes and equity in net income of affiliates	663.1	756.2	534.6
Valuation Allowance, Deferred Tax Asset, Change in Amount	(3.2)	(2.2)	1.6
Valuation Allowances and Reserves, Depreciation and Amortization	0.2	0.1	0.1
Valuation Allowances and Reserves, Other	0.0	0.3	(0.2)
Current
Federal	57.8	159.4	107.3
State	0.7	4.1	0.7
Foreign	(12.8)	11.4	20.0
Total current	45.7	174.9	128.0
Deferred
Federal	71.8	(27.8)	53.6
State	(11.4)	(12.8)	(0.2)
Foreign	26.7	5.5	(1.4)
Total Deferred	87.1	(35.1)	52.0
Total income tax provision	132.8	139.8	180.0
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]
Tax at U.S. Federal statutory rate	139.3	158.8	187.1
State income taxes, net of Federal benefit	14.9	18.1	8.8
State income tax credits, net of Federal benefit	(22.6)	(22.7)	(9.7)
Foreign rate differences	(7.1)	(6.2)	(20.6)
Research and experimentation	0.7	(5.4)	(2.6)
Domestic Production Activities Deduction	0.0	0.0	(7.1)
Interest on assessments	0.0	0.0	(0.1)
Other	(0.6)	0.2	(2.1)
Total income tax provision	$ 132.8	$ 139.8	$ 180.0
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
Tax at U.S. Federal statutory rate	21.00%	21.00%	35.00%
State income taxes, net of Federal benefit	2.30%	2.40%	1.60%
State income tax credits, net of Federal benefit	(3.40%)	(3.00%)	(1.80%)
Foreign rate differences	(1.10%)	(0.80%)	(3.80%)
Research and experimentation	(0.10%)	0.70%	0.50%
Domestic Production Activities Deduction	0.00%	0.00%	1.30%
Interest on assessments	0.00%	0.00%	0.00%
Other	(0.10%)	0.00%	(0.50%)
Total income tax provision	20.00%	18.50%	33.70%
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount	$ 1.6	$ (5.4)	$ 44.9
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Percent	0.20%	(0.70%)	8.40%
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount	$ (2.0)	$ 0.0	$ (16.2)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent	(0.30%)	0.00%	(3.00%)
Effective Tax Reconciliation- GILTI	$ 7.1	$ 1.8	$ 0.0
Effective Income Tax Reconciliation, GILTI Tax, Percent	1.10%	0.20%	0.00%
Effective Income Tax Rate Reconciliation, Excess Tax Benefit	$ (2.5)	$ (4.0)	$ (4.8)
EffectiveTaxRateRecon, ExcessTaxBenefit, Percentage	(0.40%)	(0.50%)	(0.90%)
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Amount	$ 4.0	$ 4.6	$ 2.4
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Percent	0.60%	0.60%	0.50%
Deferred Tax Assets, Tax Deferred Expense [Abstract]
Long-term contracts	$ 107.5	$ 210.2
Post-retirement benefits other than pensions	9.8	9.5
Pension and other employee benefit plans	88.5	60.4
Employee compensation accruals	39.2	36.1
Depreciation and amortization	(117.8)	(115.1)
Inventory	0.4	0.5
State income tax credits	108.3	94.1
Accruals and reserves	40.3	46.2
Deferred production	0.0	(1.8)
Net operating loss carryforward	0.4	0.4
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, Tax	0.2	0.0
Other	8.6	(2.3)
Net deferred tax asset	108.4	217.4
Valuation allowance	(10.2)	(13.2)
Net deferred tax asset	98.2	204.2
Components of Deferred Tax Assets and Liabilities [Abstract]
Non-current deferred tax assets	106.5	205.0
Non-current deferred tax liabilities	(8.3)	(0.8)
Net non-current deferred tax assets	98.2	204.2
Total deferred tax asset	98.2	204.2
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning Balance	7.2	6.7	$ 6.3
Gross increases related to current period tax positions	0.4	0.0	0.0
Gross increases related to prior period tax positions	0.0	0.5	0.4
Gross decreases related to prior period tax positions	(2.2)	0.0	0.0
Statute of limitations' expiration	0.0	0.0	0.0
Settlements	0.0	0.0	0.0
Ending Balance	$ 5.4	$ 7.2	$ 6.7