Unaudited Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 53,137	$ 21,482	$ 139,909	$ 95,439
Foreign currency translation adjustment	(29)	6	(495)	72
Other comprehensive income (loss), before tax	(29)	6	(495)	72
Income tax expense on other comprehensive income (loss)	0	0	0	0
Other comprehensive income (loss), net of tax	(29)	6	(495)	72
Comprehensive income	$ 53,108	$ 21,488	$ 139,414	$ 95,511