Restructuring and Acquisition-Related Costs - Restructuring Reserve Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 58.4	$ 39.8	$ 44.2
Minimum [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and related cost, expected cost remaining	50.0
Maximum [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and related cost, expected cost remaining	65.0
Driveline [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	19.3	6.4	3.4
Metal Forming [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	16.0	21.5	37.6
Casting [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges		0.7	0.1
Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	22.3	19.4	2.5
Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	36.1	20.4	11.7
2020 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	47.8
Asset Impairment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 0.0	$ 0.0	$ 30.0