CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 70,617	$ 57,205	$ 165,560	$ 123,120
Other comprehensive income (loss):
Unrealized gains (losses) on investments	167	1,293	(1,400)	4,317
Unrealized gains (losses) on cash flow hedges	(2,029)	(8,732)	2,750	(33,106)
Total unrealized gains (losses)	(1,862)	(7,439)	1,350	(28,789)
Income tax (expense) benefit	701	2,855	(531)	10,995
Other comprehensive income (loss), net of tax (expense) benefit	(1,161)	(4,584)	819	(17,794)
Total comprehensive income	$ 69,456	$ 52,621	$ 166,379	$ 105,326