Restructuring - Restructuring Activities (Details) - Restructuring 2017 - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		14 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018
Restructuring Reserve [Roll Forward]
Restructuring reserve, start			$ 5,189
Restructuring and related cost, incurred cost	$ 7,423	$ 6,737	15,580	$ 6,737
Restructuring reserve, foreign currency translation gain (loss)			(34)
Payments for restructuring			9,424	2,453	$ 21,100
Restructuring reserve, settled without cash			8,150	77	104,600
Restructuring reserve, end	3,161	4,207	3,161	4,207	3,161
Severance and benefit related costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, start			3,864
Restructuring and related cost, incurred cost			3,217	5,070
Restructuring reserve, foreign currency translation gain (loss)			(30)
Payments for restructuring			4,754	1,639
Restructuring reserve, settled without cash			0	0
Restructuring reserve, end	2,297	3,431	2,297	3,431	2,297
Lease and contract termination costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, start			650
Restructuring and related cost, incurred cost			1,202	340
Restructuring reserve, foreign currency translation gain (loss)			(4)
Payments for restructuring			1,337	264
Restructuring reserve, settled without cash			0	0
Restructuring reserve, end	511	76	511	76	511
Relocation and other moving costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, start			0
Restructuring and related cost, incurred cost			129	29
Restructuring reserve, foreign currency translation gain (loss)			0
Payments for restructuring			129	29
Restructuring reserve, settled without cash			0	0
Restructuring reserve, end	0	0	0	0	0
Other restructuring costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, start			675
Restructuring and related cost, incurred cost			11,032	1,298
Restructuring reserve, foreign currency translation gain (loss)			0
Payments for restructuring			3,204	521
Restructuring reserve, settled without cash			8,150	77
Restructuring reserve, end	$ 353	$ 700	$ 353	$ 700	$ 353