Impairment, Restructuring and Other Exit Costs - Restructuring Liability (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Restructuring Reserve [Roll Forward]
Restructuring charges accrued during the period	$ 0	$ 0	$ 26,392	$ 106,189
Severance
Restructuring Reserve [Roll Forward]
Restructuring reserve balance at the beginning of the period			16,481	30,479	$ 30,479
Restructuring charges accrued during the period					3,720
Cash payments / settlements during the period			(16,378)		(18,858)
Currency translation			(103)		1,140
Restructuring reserve balance at the end of the period	0		0		16,481
Lease Exit Costs
Restructuring Reserve [Roll Forward]
Restructuring reserve balance at the beginning of the period			106	564	564
Restructuring charges accrued during the period					334
Cash payments / settlements during the period			(106)		(793)
Currency translation			0		1
Restructuring reserve balance at the end of the period	0		0		106
Total
Restructuring Reserve [Roll Forward]
Restructuring reserve balance at the beginning of the period			16,587	31,043	31,043
Restructuring charges accrued during the period					4,054
Cash payments / settlements during the period			(16,484)		(19,651)
Currency translation			(103)		1,141
Restructuring reserve balance at the end of the period	$ 0		$ 0		$ 16,587
AMECO
Restructuring [Line Items]
Restructuring related severance costs		$ 4,000		$ 4,000