Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Operating Activities
Net income	$ 48.8	$ 30.2
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	35.4	35.4
Amortization of debt discount and deferred financing costs	4.4	4.2
Stock-based compensation	6.7	10.2
Retirement benefits, net	6.7	15.4
Insurance proceeds	(1.9)	0.0
Other, net	(0.1)	0.3
Changes in assets and liabilities, net of effects from acquisition in 2017:
Accounts receivable	(40.7)	(50.3)
Contract assets	(7.5)	(9.7)
Other current assets, net	16.3	12.2
Recoverable environmental remediation costs	5.3	10.1
Other noncurrent assets	(1.5)	(31.5)
Accounts payable	(9.7)	12.6
Contract liabilities	(58.1)	(43.0)
Other current liabilities	21.8	13.6
Deferred income taxes	2.3	15.9
Reserves for environmental remediation costs	(7.7)	(10.8)
Other noncurrent liabilities and other	4.0	22.9
Net Cash Provided by Operating Activities	24.5	37.7
Investing Activities
Purchases of marketable securities	(44.7)	0.0
Sales of marketable securities	20.1	0.0
Purchase of Coleman Aerospace	0.0	(15.0)
Insurance proceeds	1.9	0.0
Capital expenditures	(12.2)	(6.1)
Net Cash Used in Investing Activities	(34.9)	(21.1)
Financing Activities
Debt repayments	(10.3)	(10.0)
Repurchase of shares for withholding taxes and option costs under employee equity plans	(2.1)	(5.7)
Proceeds from shares issued under equity plans	2.5	2.4
Net Cash Used in Financing Activities	(9.9)	(13.3)
Net (Decrease) Increase in Cash and Cash Equivalents	(20.3)	3.3
Cash and Cash Equivalents at Beginning of Period	535.0	410.3
Cash and Cash Equivalents at End of Period	514.7	413.6
Supplemental disclosures of cash flow information
Cash paid for interest	11.9	11.4
Cash paid for income taxes	15.2	0.5
Cash refund for income taxes	4.6	21.3
Conversion of debt to common stock	0.0	35.6
Non-cash fixed asset additions and capital leases	$ 14.2	$ 0.2