CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 126,254	$ 94,943
Other comprehensive income (loss):
Unrealized losses on investments	(4,127)	(1,567)
Unrealized gains on cash flow hedges	20,290	4,779
Total unrealized gains	16,163	3,212
Income tax expense	(3,902)	(1,232)
Other comprehensive income, net of tax expense	12,261	1,980
Total comprehensive income	$ 138,515	$ 96,923