Unaudited Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 42,682	$ 36,624	$ 86,772	$ 73,957
Foreign currency translation adjustment	104	38	(466)	66
Other comprehensive income (loss), before tax	104	38	(466)	66
Income tax expense on other comprehensive income (loss)	0	0	0	0
Other comprehensive income (loss), net of tax	104	38	(466)	66
Comprehensive income	$ 42,786	$ 36,662	$ 86,306	$ 74,023