Stockholders' Equity - Changes in AOCI (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Changes in the balances of each component of AOCI
Balance at the beginning of the period	$ 840,093	$ 601,704	$ 714,615
Total other comprehensive income (loss), net of tax	8	35	429
Balance at the end of the period	437,775	840,093	601,704
Accumulated Other Comprehensive Income
Changes in the balances of each component of AOCI
Balance at the beginning of the period	1,812	1,777	1,348
Other comprehensive income (loss) before reclassifications			(25)
Amounts reclassified from AOCI			454
Total other comprehensive income (loss), net of tax	8	35	429
Balance at the end of the period	1,820	1,812	1,777
Foreign Currency Translation
Changes in the balances of each component of AOCI
Balance at the beginning of the period	1,839	1,797	2,246
Other comprehensive income (loss) before reclassifications			(19)
Amounts reclassified from AOCI			(430)
Total other comprehensive income (loss), net of tax	(3)	42	(449)
Balance at the end of the period	1,836	1,839	1,797
Minimum pension liability
Changes in the balances of each component of AOCI
Balance at the beginning of the period			(866)
Amounts reclassified from AOCI			866
Total other comprehensive income (loss), net of tax			866
Unrealized Gains (Losses) on Available for Sale Securities
Changes in the balances of each component of AOCI
Balance at the beginning of the period	(27)	(20)	(32)
Other comprehensive income (loss) before reclassifications			(6)
Amounts reclassified from AOCI			18
Total other comprehensive income (loss), net of tax	11	(7)	12
Balance at the end of the period	$ (16)	$ (27)	$ (20)