Basis of Preparation - Balance Sheet Impact (Details) - USD ($) $ in Millions	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Assets
Accounts receivable, net of allowances	$ 204.4	$ 222.7	$ 222.7
Inventories, net	233.5	197.3	208.9
Unbilled contract revenue	41.2	43.5	37.0
Prepaid expenses	14.2	13.8	15.4
Other current assets	19.2		27.4
Liabilities
Accounts payable	128.6	114.1	113.9
Customer advances and billings in excess of contract revenue	108.9	100.3	110.2
Other current liabilities	39.2	41.5	41.4
Long-term deferred tax liabilities	63.4	63.1	62.5
Equity
Retained earnings	384.7	366.6	364.3
Balances without adoption of ASC 606
Assets
Inventories, net			208.9
Unbilled contract revenue			37.0
Prepaid expenses			15.4
Liabilities
Accounts payable			113.9
Customer advances and billings in excess of contract revenue			110.2
Other current liabilities			41.4
Long-term deferred tax liabilities			62.5
Equity
Retained earnings			$ 364.3
Balances without adoption of ASC 606 | ASU 2014-09
Assets
Accounts receivable, net of allowances	202.7
Inventories, net	255.5
Unbilled contract revenue	29.5
Other current assets	19.1
Liabilities
Customer advances and billings in excess of contract revenue	123.5
Other current liabilities	37.7
Long-term deferred tax liabilities	62.3
Equity
Retained earnings	381.2
Adjustments due to ASC 606 | ASU 2014-09
Assets
Accounts receivable, net of allowances	1.7
Inventories, net	(22.0)	(11.6)
Unbilled contract revenue	11.7	6.5
Prepaid expenses		(1.6)
Other current assets	0.1
Liabilities
Accounts payable		0.2
Customer advances and billings in excess of contract revenue	(14.6)	(9.9)
Other current liabilities	1.5	0.1
Long-term deferred tax liabilities	1.1	0.6
Equity
Retained earnings	$ 3.5	$ 2.3