Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net income	$ 241,041	$ 324,089	$ 407,798	$ 494,841
Other comprehensive income, net of tax:
Change in value of derivatives	25	30	50	50
Other comprehensive income	25	30	50	50
Comprehensive income (loss)	$ 241,066	$ 324,119	$ 407,848	$ 494,891