CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 143,440	$ 150,286	$ 292,474	$ 271,045	$ 419,222
Other comprehensive (loss) income
Foreign currency translation	(22,715)	14,393	(33,383)	3,521
Change in unrealized gain on marketable securities	69	(6,395)	250	(5,046)
Other	(1,617)	(2,175)	(3,497)	(1,416)
Total other comprehensive (loss) income	(24,263)	5,823	(36,630)	(2,941)	$ (20,686)
Comprehensive income	119,177	156,109	255,844	268,104
Comprehensive income attributable to noncontrolling interest	278	465	332	782
Comprehensive income attributable to common stockholders	$ 118,899	$ 155,644	$ 255,512	$ 267,322