Amount before tax of gain (loss) recognized on the sale or disposal of a disposal group. Excludes discontinued operations.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Business Segments - Additional Information (Details) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) segment	Sep. 30, 2018 USD ($)	Jun. 03, 2019 USD ($)	Dec. 31, 2018 USD ($)
Restructuring Cost and Reserve [Line Items]
Gain on asset sales, net	$ 68.2		$ 0.0	$ 89.8	$ 0.0
Number of business segments \| segment				2
Goodwill	523.8			$ 523.8			$ 534.7
Gain on the sale of oil and gas rights	62.4			91.7
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal				(1.8)	$ 0.0
Cast Products
Restructuring Cost and Reserve [Line Items]
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	6.2
Forged Products
Restructuring Cost and Reserve [Line Items]
Goodwill						$ 10.4
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	$ (0.4)	$ (7.7)		$ (8.1)