Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net income	$ 602,703	$ 494,090	$ 474,338
Other comprehensive income, net of tax:
Change in value of derivatives	83	81	105
Other comprehensive income	83	81	105
Comprehensive income	$ 602,786	$ 494,171	$ 474,443