Acquisitions - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Millions							4 Months Ended	12 Months Ended
	Dec. 31, 2021	Sep. 01, 2021	Nov. 20, 2020	Jan. 11, 2020	Nov. 20, 2019	Jan. 11, 2019	Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Nov. 20, 2020	Jan. 11, 2020	Dec. 31, 2019
Recognized amounts of identifiable assets acquired and liabilities assumed:
Other intangible assets		$ 1,181.8
Goodwill	$ 2,199.0						$ 2,199.0	$ 2,199.0	$ 1,641.7			$ 1,619.8
Measurement period adjustments, goodwill								(339.6)	$ (2.3)
ASP Henry Holdings, Inc.
Acquisitions
Consideration transferred	1,605.6	1,608.2
Recognized amounts of identifiable assets acquired and liabilities assumed:
Cash and cash equivalents	34.3	34.3					34.3	34.3
Receivables, net	79.0	79.0					79.0	79.0
Inventories	51.5	59.4					51.5	51.5
Prepaid expenses and other current assets	10.3	10.5					10.3	10.3
Property, plant and equipment	61.8	53.6					61.8	61.8
Other intangible assets	1,181.8	735.1					1,181.8	1,181.8
Other long-term assets	11.3	3.6					11.3	11.3
Accounts payable	(75.7)	(77.9)					(75.7)	(75.7)
Accrued and other current liabilities	(29.1)	(28.7)					(29.1)	(29.1)
Short-term debt	(1.0)	(1.0)					(1.0)	(1.0)
Contract liabilities	(2.6)	(2.6)					(2.6)	(2.6)
Other long-term debt	(0.8)	(0.8)					(0.8)	(0.8)
Other long-term liabilities	(13.6)	(5.9)					(13.6)	(13.6)
Deferred income taxes	(265.2)	(153.4)					(265.2)	(265.2)
Total identifiable net assets	1,042.0	705.2					1,042.0	1,042.0
Goodwill	$ 563.6	$ 903.0					563.6	$ 563.6
ASP Henry Holdings, Inc. | Adjustment
Acquisitions
Measurement period adjustments, total consideration transferred							(2.6)
Recognized amounts of identifiable assets acquired and liabilities assumed:
Measurement period adjustments, inventories, net							(7.9)
Measurement period adjustments, prepaid expenses and other current assets							(0.2)
Measurement period adjustments, property, plant and equipment							8.2
Measurement period adjustments, intangibles, net							446.7
Measurement period adjustments, other long-term assets							7.7
Measurement period adjustments, accounts payable							2.2
Measurement period adjustments, accrued and other current liabilities							(0.4)
Measurement period adjustments, other long-term liabilities							(7.7)
Measurement period adjustments, deferred income taxes							(111.8)
Measurement period adjustments, total identifiable net assets							336.8
Measurement period adjustments, goodwill							$ (339.4)
Providien
Acquisitions
Consideration transferred			$ 331.3		$ 332.1
Recognized amounts of identifiable assets acquired and liabilities assumed:
Cash and cash equivalents			3.4		3.4					$ 3.4
Receivables, net			9.8		9.8					9.8
Inventories			2.4		2.7					2.4
Contract assets			24.6		29.1					24.6
Prepaid expenses and other current assets			1.4		2.3					1.4
Property, plant and equipment			12.9		12.9					12.9
Other intangible assets			132.7		135.4					132.7
Other long-term assets			6.8		7.1					6.8
Accounts payable			(5.8)		(6.0)					(5.8)
Income tax payable			0.1		(0.7)					0.1
Accrued and other current liabilities			(7.0)		(7.0)					(7.0)
Other long-term liabilities			(7.0)		(8.1)					(7.0)
Deferred income taxes			(19.0)		(27.1)					(19.0)
Total identifiable net assets			155.3		153.8					155.3
Goodwill			$ 176.0		$ 178.3					176.0
Providien | Adjustment
Acquisitions
Measurement period adjustments, total consideration transferred										(0.8)
Recognized amounts of identifiable assets acquired and liabilities assumed:
Measurement period adjustments, inventories, net										(0.3)
Measurement period adjustments, contract assets										(4.5)
Measurement period adjustments, prepaid expenses and other current assets										(0.9)
Measurement period adjustments, intangibles, net										(2.7)
Measurement period adjustments, other long-term assets										(0.3)
Measurement period adjustments, accounts payable										0.2
Measurement period adjustments, income tax payable										0.8
Measurement period adjustments, other long-term liabilities										1.1
Measurement period adjustments, deferred income taxes										8.1
Measurement period adjustments, total identifiable net assets										1.5
Measurement period adjustments, goodwill										$ (2.3)
Petersen Aluminum
Acquisitions
Consideration transferred				$ 207.2		$ 207.2
Recognized amounts of identifiable assets acquired and liabilities assumed:
Cash and cash equivalents				5.2		5.2					$ 5.2
Receivables, net				11.5		11.5					11.5
Inventories				39.2		39.5					39.2
Prepaid expenses and other current assets				2.1		2.1					2.1
Property, plant and equipment				17.8		17.8					17.8
Other intangible assets				110.1		109.3					110.1
Other long-term assets				9.5		9.5					9.5
Accounts payable				(5.9)		(5.9)					(5.9)
Income tax payable				1.7		1.7					1.7
Accrued and other current liabilities				(8.7)		(8.7)					(8.7)
Other long-term liabilities				(12.5)		(12.4)					(12.5)
Deferred income taxes				(25.6)		(25.4)					(25.6)
Total identifiable net assets				144.4		144.2					144.4
Goodwill				$ 62.8		$ 63.0					62.8
Petersen Aluminum | Adjustment
Recognized amounts of identifiable assets acquired and liabilities assumed:
Measurement period adjustments, inventories, net											(0.3)
Measurement period adjustments, intangibles, net											0.8
Measurement period adjustments, other long-term liabilities											(0.1)
Measurement period adjustments, deferred income taxes											(0.2)
Measurement period adjustments, total identifiable net assets											0.2
Measurement period adjustments, goodwill											$ (0.2)