Description of Business and Basis of Presentation - Effect of New Accounting Pronouncement (Details) - USD ($) $ in Millions	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Trade receivables, net of allowance	$ 287.6	$ 285.1	$ 316.4
Inventories	305.4	293.8	190.2
Other current assets	55.0	55.0	48.0
Deferred income taxes	14.4	15.4	13.1
Total Assets	1,498.0	1,473.0	1,391.4
Advance and progress payments	245.3	240.7	127.6
Other current liabilities	132.7	94.1	146.2
Other long-term liabilities	45.2	48.3	49.5
Retained earnings	303.4	305.7	333.7
Total Liabilities and Stockholders' Equity	1,498.0	1,473.0	1,391.4
As Reported
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Trade receivables, net of allowance	321.2		316.4
Inventories	229.5		190.2
Other current assets	47.2		48.0
Deferred income taxes	12.6		13.1
Total Assets	1,446.1		1,391.4
Advance and progress payments	177.3		127.6
Other current liabilities	130.9		96.4
Other long-term liabilities	47.0		49.5
Retained earnings	321.7		333.7
Total Liabilities and Stockholders' Equity	1,446.1		$ 1,391.4
Accounting Standards Update 2014-09 | Adjustments due to Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Trade receivables, net of allowance	33.6	(31.3)
Inventories	(75.9)	103.6
Other current assets	(7.8)	7.0
Deferred income taxes	(1.8)	2.3
Total Assets	(51.9)	81.6
Advance and progress payments	(68.0)	113.1
Other current liabilities	(1.8)	(2.3)
Other long-term liabilities	1.8	(1.2)
Retained earnings	18.3	(28.0)
Total Liabilities and Stockholders' Equity	$ (51.9)	$ 81.6