CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 487,476	$ 288,934	$ 250,327
Other comprehensive income (loss):
Unrealized losses on investments	(2,561)	(716)	(1,792)
Unrealized gains (losses) on cash flow hedges	11,907	19,195	13,764
Total unrealized gains (losses)	9,346	18,479	11,972
Income tax (expense) benefit	(2,333)	(7,060)	(4,584)
Other comprehensive income (losses), net of tax (expense) benefit	7,013	11,419	7,388
Total comprehensive income	$ 494,489	$ 300,353	$ 257,715