Restructuring - Restructuring and Related Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring expense	$ 1,659	$ 0	$ 6,632	$ 0
Restructuring Reserve [Roll Forward]
Ending balance of total accrued restructuring	4,609		4,609
Employee severance costs
Restructuring Cost and Reserve [Line Items]
Restructuring expense	1,556		5,719
Restructuring Reserve [Roll Forward]
Beginning balance of accrued restructuring	4,163		0
Additional restructuring accrual	1,556		5,719
Payments for restructuring	(1,235)		(1,235)
Ending balance of total accrued restructuring	4,609		4,609
Asset write-downs & other costs
Restructuring Cost and Reserve [Line Items]
Restructuring expense	103		913
Restructuring Reserve [Roll Forward]
Beginning balance of accrued restructuring	125		0
Additional restructuring accrual	103		303
Payments for restructuring	$ (103)		$ (178)