Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 176,293	$ 20,405	$ 25,625
Other comprehensive income (loss), net of tax:
Change in foreign currency translation	(60)
Change in fair value of interest rate swap agreements	1,530	1,138	(1,977)
Termination of interest rate swap agreements	1,447
Total other comprehensive income (loss)	2,917	1,138	(1,977)
Comprehensive income	$ 179,210	$ 21,543	$ 23,648