Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Operating Activities
Net income	$ 105.7	$ 102.3
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	44.4	49.7
Amortization of debt discount and deferred financing costs	4.5	7.4
Stock-based compensation	10.6	13.2
Retirement benefits, net	10.2	18.9
Loss on debt	10.5	0.0
Other, net	(0.9)	0.2
Changes in assets and liabilities:
Accounts receivable	(9.6)	(69.9)
Contract assets	(39.1)	(49.2)
Other current assets	15.3	7.3
Recoverable environmental remediation costs	(1.8)	6.0
Other noncurrent assets	16.9	6.9
Accounts payable	(2.8)	(33.6)
Contract liabilities	(65.0)	81.1
Other current liabilities	2.9	(12.0)
Deferred income taxes	0.0	4.2
Reserves for environmental remediation costs	2.7	(5.1)
Other noncurrent liabilities and other	(9.1)	11.2
Net Cash Provided by Operating Activities	95.4	138.6
Investing Activities
Purchases of marketable securities	(1.9)	(26.5)
Sales of marketable securities	0.0	25.0
Capital expenditures	(17.3)	(31.0)
Net Cash Used in Investing Activities	(19.2)	(32.5)
Financing Activities
Dividend payments	(428.5)	0.0
Debt repayments	(175.5)	(14.7)
Repurchase of shares for withholding taxes and option costs under equity plans	(4.5)	(8.8)
Proceeds from shares issued under equity plans	7.7	7.1
Purchase of treasury stock	0.0	(12.3)
Net Cash Used in Financing Activities	(600.8)	(28.7)
Net (Decrease) Increase in Cash, Cash Equivalents and Restricted Cash	(524.6)	77.4
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	1,152.5	935.6
Cash, Cash Equivalents and Restricted Cash at End of Period	627.9	1,013.0
Supplemental disclosures of cash flow information
Cash paid for interest	9.8	13.5
Cash paid for income taxes, net of refunds	$ 19.5	$ 35.5