CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 76,371	$ 56,965	$ 241,931	$ 180,085
Other comprehensive income (loss):
Unrealized gains (losses) on investments	734	406	(666)	4,723
Unrealized gains (losses) on cash flow hedges	4,814	9,324	7,564	(23,782)
Total unrealized gains (losses)	5,548	9,730	6,898	(19,059)
Income tax (expense) benefit	(2,113)	(3,690)	(2,644)	7,305
Other comprehensive income (loss), net of tax (expense) benefit	3,435	6,040	4,254	(11,754)
Total comprehensive income	$ 79,806	$ 63,005	$ 246,185	$ 168,331