CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 56,965	$ 45,724	$ 180,085	$ 184,439
Other comprehensive income (loss):
Unrealized gains (losses) on investments	406	2,008	4,723	(499)
Unrealized gains (losses) on cash flow hedges	9,324	(21,751)	(23,782)	(19,284)
Total unrealized gains (losses)	9,730	(19,743)	(19,059)	(19,783)
Income tax (expense) benefit	(3,690)	7,676	7,305	7,661
Other comprehensive income (loss), net of tax (expense) benefit	6,040	(12,067)	(11,754)	(12,122)
Total comprehensive income	$ 63,005	$ 33,657	$ 168,331	$ 172,317