Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ (19,712)	$ 12,161	$ 175,698
Other comprehensive income (loss), net of tax:
Change in foreign currency translation	(147)	(352)	(60)
Change in fair value of marketable securities	1,428	(1,000)
Change in fair value of interest rate swap agreements			1,530
Termination of interest rate swap agreements			1,447
Total other comprehensive income (loss)	1,281	(1,352)	2,917
Comprehensive income (loss)	$ (18,431)	$ 10,809	$ 178,615