CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 109,832	$ 70,617	$ 236,086	$ 165,560
Other comprehensive income (loss):
Unrealized gains (losses) on investments	42	167	(4,085)	(1,400)
Unrealized gains (losses) on cash flow hedges	10,014	(2,029)	30,304	2,750
Total unrealized gains (losses)	10,056	(1,862)	26,219	1,350
Income tax (expense) benefit	(2,441)	701	(6,343)	(531)
Other comprehensive income (loss), net of tax (expense) benefit	7,615	(1,161)	19,876	819
Total comprehensive income	$ 117,447	$ 69,456	$ 255,962	$ 166,379