Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Operating Activities
Net income	$ 27.8	$ 27.8
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation and amortization	13.3	14.4
Stock-based compensation	4.5	(0.9)
Retirement benefits, net	(3.3)	(6.6)
Other, net	(0.5)	0.9
Changes in assets and liabilities:
Accounts receivable	(50.8)	(82.8)
Contract assets	34.1	(17.8)
Other current assets	38.9	5.9
Recoverable environmental remediation costs	5.4	5.5
Other noncurrent assets	0.5	6.8
Accounts payable	(20.3)	(19.0)
Contract liabilities	(27.1)	0.2
Other current liabilities	(49.6)	45.3
Deferred income taxes	(31.2)	(45.8)
Reserves for environmental remediation costs	(5.2)	(2.7)
Other noncurrent liabilities	30.7	(6.2)
Net Cash Used in Operating Activities	(32.8)	(75.0)
Investing Activities
Capital expenditures	(1.6)	(2.2)
Net Cash Used in Investing Activities	(1.6)	(2.2)
Financing Activities
Dividend payments	(0.5)	(1.2)
Debt repayments	(3.9)	(7.1)
Repurchase of shares for withholding taxes under equity plans	(14.1)	(4.3)
Proceeds from shares issued under equity plans	3.3	0.3
Net Cash Used in Financing Activities	(15.2)	(12.3)
Net Decrease in Cash, Cash Equivalents and Restricted Cash	(49.6)	(89.5)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	325.2	703.4
Cash, Cash Equivalents and Restricted Cash at End of Period	275.6	613.9
Supplemental disclosures of cash flow information
Cash paid for interest	$ 5.4	$ 2.6