Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net income	$ 289,535	$ 177,539	$ 784,375	$ 369,807
Other comprehensive income, net of tax:
Change in value of derivatives	25	20	75	61
Other comprehensive income	25	20	75	61
Comprehensive income (loss)	$ 289,560	$ 177,559	$ 784,450	$ 369,868