Restructuring Charges - Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restructuring accruals roll forward
Balance at the beginning of the period	$ 1,520	$ 1,796	$ 824
Provision	7,395	9,971	5,642
Changes in estimate			(2)
Payments	(6,702)	(10,247)	(4,668)
Balance at the end of the period	2,213	1,520	1,796
Personnel severance and related costs
Restructuring accruals roll forward
Balance at the beginning of the period	1,520	1,796	824
Provision	4,681	4,714	4,544
Changes in estimate			(2)
Payments	(4,058)	(4,990)	(3,570)
Balance at the end of the period	2,143	1,520	1,796
Facility Closing Costs
Restructuring accruals roll forward
Provision	2,714	5,257	1,098
Payments	(2,644)	$ (5,257)	$ (1,098)
Balance at the end of the period	$ 70