Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 31,821	$ 47,565	$ 38,822	$ 21,163	$ 29,203	$ 41,419	$ 35,813	$ 21,594	$ 139,371	$ 128,029	$ 123,160
Other comprehensive income (loss), net of tax:
Amortization of loss on cash flow hedge									862	862	861
Foreign currency translation adjustment									(606)	(2,669)	(1,615)
Other comprehensive income (loss), net of tax									256	(1,807)	(754)
Comprehensive income									$ 139,627	$ 126,222	$ 122,406