Accumulated Other Comprehensive Loss - Changes in Accumulated Other Comprehensive Loss, Net of Tax (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ (185,477)	$ (183,772)	$ (259,917)	$ (258,601)	$ (183,772)	$ (258,601)
Other comprehensive loss before reclassification					(659)	(1,014)
Amounts reclassified from accumulated other comprehensive loss					431	431
Net current period other comprehensive income (loss)	(236)	8	(1,653)	1,070	(228)	(583)
Ending balance	(122,660)	(185,477)	(203,952)	(259,917)	(122,660)	(203,952)
Loss on Cash Flow Hedge
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(1,436)		(2,298)	(1,436)	(2,298)
Other comprehensive loss before reclassification					0	0
Amounts reclassified from accumulated other comprehensive loss					431	431
Net current period other comprehensive income (loss)					431	431
Ending balance	(1,005)		(1,867)		(1,005)	(1,867)
Foreign Currency Items
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(4,010)		(2,401)	(4,010)	(2,401)
Other comprehensive loss before reclassification					(659)	(1,014)
Amounts reclassified from accumulated other comprehensive loss					0	0
Net current period other comprehensive income (loss)					(659)	(1,014)
Ending balance	(4,669)		(3,415)		(4,669)	(3,415)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(5,438)	(5,446)	(3,629)	(4,699)	(5,446)	(4,699)
Net current period other comprehensive income (loss)	(236)	8	(1,653)	1,070
Ending balance	$ (5,674)	$ (5,438)	$ (5,282)	$ (3,629)	$ (5,674)	$ (5,282)