Revision of Previously Issued Financial Statements - Condensed Consolidated Balance Sheet (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Jan. 01, 2021	Dec. 31, 2020	Jan. 01, 2020	Jan. 01, 2019
Reclassification [Line Items]
Cash and cash equivalents	$ 610.9	$ 700.4
Restricted cash	3.0	3.0
Marketable securities	10.1	10.6
Accounts receivable	143.4	60.6
Contract assets	372.0	354.2
Other current assets	93.6	99.5
Total Current Assets	1,233.0	1,228.3
Right-of-use assets	49.8	52.6
Property, plant and equipment, net	413.3	421.1
Recoverable environmental remediation costs	220.7	226.2
Deferred income taxes	101.5	55.6
Goodwill	161.4	161.4
Intangible assets	33.1	34.9
Other noncurrent assets	236.3	243.3
Total Noncurrent Assets	1,216.1	1,195.1
Total Assets	2,449.1	2,423.4
Current portion of long-term debt	177.3	166.7
Accounts payable	115.1	132.2
Reserves for environmental remediation costs	41.2	37.7
Contract liabilities	366.7	366.5
Other current liabilities	213.1	172.7
Total Current Liabilities	913.4	875.8
Long-term debt	285.7	294.6
Reserves for environmental remediation costs	252.5	258.7
Pension benefits	242.9	255.9
Operating lease liabilities	38.8	41.3
Other noncurrent liabilities	165.9	173.8
Total Noncurrent Liabilities	985.8	1,024.3
Total Liabilities	1,899.2	1,900.1
Common stock, par value of $0.10; 150.0 million shares authorized; 80.3 million shares outstanding as of March 31, 2022; 80.1 million shares outstanding as of December 31, 2021	8.0	8.0
Other capital	572.7	578.1		$ 20.9		$ 20.9	$ 20.9
Treasury stock at cost	(64.4)	(64.4)
Retained earnings	129.4	102.6		$ (7.8)		$ 8.0	$ 7.9
Accumulated other comprehensive loss, net of income taxes	(95.8)	(101.0)
Total Stockholders’ Equity	549.9	523.3	$ 263.9		$ 220.4
Total Liabilities and Stockholders’ Equity	$ 2,449.1	2,423.4
Previously Reported
Reclassification [Line Items]
Cash and cash equivalents		700.4
Restricted cash		3.0
Marketable securities		10.6
Accounts receivable		60.6
Contract assets		354.2
Other current assets		107.8
Total Current Assets		1,236.6
Right-of-use assets		52.6
Property, plant and equipment, net		421.1
Recoverable environmental remediation costs		226.2
Deferred income taxes		57.5
Goodwill		161.4
Intangible assets		34.9
Other noncurrent assets		243.3
Total Noncurrent Assets		1,197.0
Total Assets		2,433.6
Current portion of long-term debt		166.7
Accounts payable		132.2
Reserves for environmental remediation costs		37.7
Contract liabilities		366.5
Other current liabilities		172.7
Total Current Liabilities		875.8
Long-term debt		294.6
Reserves for environmental remediation costs		258.7
Pension benefits		255.9
Operating lease liabilities		41.3
Other noncurrent liabilities		173.8
Total Noncurrent Liabilities		1,024.3
Total Liabilities		1,900.1
Common stock, par value of $0.10; 150.0 million shares authorized; 80.3 million shares outstanding as of March 31, 2022; 80.1 million shares outstanding as of December 31, 2021		8.0
Other capital		599.0
Treasury stock at cost		(64.4)
Retained earnings		91.9
Accumulated other comprehensive loss, net of income taxes		(101.0)
Total Stockholders’ Equity		533.5	277.0
Total Liabilities and Stockholders’ Equity		2,433.6
Adjustments
Reclassification [Line Items]
Cash and cash equivalents		0.0
Restricted cash		0.0
Marketable securities		0.0
Accounts receivable		0.0
Contract assets		0.0
Other current assets		(8.3)
Total Current Assets		(8.3)
Right-of-use assets		0.0
Property, plant and equipment, net		0.0
Recoverable environmental remediation costs		0.0
Deferred income taxes		(1.9)
Goodwill		0.0
Intangible assets		0.0
Other noncurrent assets		0.0
Total Noncurrent Assets		(1.9)
Total Assets		(10.2)
Current portion of long-term debt		0.0
Accounts payable		0.0
Reserves for environmental remediation costs		0.0
Contract liabilities		0.0
Other current liabilities		0.0
Total Current Liabilities		0.0
Long-term debt		0.0
Reserves for environmental remediation costs		0.0
Pension benefits		0.0
Operating lease liabilities		0.0
Other noncurrent liabilities		0.0
Total Noncurrent Liabilities		0.0
Total Liabilities		0.0
Common stock, par value of $0.10; 150.0 million shares authorized; 80.3 million shares outstanding as of March 31, 2022; 80.1 million shares outstanding as of December 31, 2021		0.0
Other capital		(20.9)
Treasury stock at cost		0.0
Retained earnings		10.7
Accumulated other comprehensive loss, net of income taxes		0.0
Total Stockholders’ Equity		(10.2)	$ (13.1)
Total Liabilities and Stockholders’ Equity		$ (10.2)