Revenue Recognition - Impact on Balance Sheet (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
Accounts payable, trade and other	156.8		157.1
Advance and progress payments	245.3	240.7	127.6
Other current liabilities	132.7	94.1	146.2
Other 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
Balances without Adoption
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
Accounts payable, trade and other	154.6
Advance and progress payments	177.3		127.6
Other current liabilities	130.9		96.4
Other liabilities	47.0		49.5
Retained earnings	321.7		333.7
Total Liabilities and Stockholders' Equity	1,446.1		$ 1,391.4
Adjustments due to Topic 606 | Accounting Standards Update 2014-09
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
Accounts payable, trade and other	(2.2)
Advance and progress payments	(68.0)	113.1
Other current liabilities	(1.8)	(2.3)
Other liabilities	1.8	(1.2)
Retained earnings	18.3	(28.0)
Total Liabilities and Stockholders' Equity	$ (51.9)	$ 81.6