Restructuring - Summary of Restructuring Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restructuring Cost And Reserve [Line Items]
Balance at January 1, 2017	$ 1,188
Charges to expense	119	$ 7,553	$ 0
Cash payments	(1,261)	(4,372)
Non-cash utilization	(16)	(1,993)
Balance at December 31, 2017	30	1,188
Employee Reduction [Member]
Restructuring Cost And Reserve [Line Items]
Balance at January 1, 2017	1,098
Charges to expense	31	3,022
Cash payments	(1,099)	(1,924)
Balance at December 31, 2017	30	1,098
Accelerated Depreciation [Member]
Restructuring Cost And Reserve [Line Items]
Charges to expense	16	1,993
Non-cash utilization	(16)	(1,993)
Other Exit Costs [Member]
Restructuring Cost And Reserve [Line Items]
Balance at January 1, 2017	90
Charges to expense	72	2,538
Cash payments	$ (162)	(2,448)
Balance at December 31, 2017		$ 90