CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 150,350	$ 138,566	$ 271,157	$ 259,840	$ 477,186
Other comprehensive income (loss):
Foreign currency translation	14,393	7,719	3,521	4,979
Change in unrealized gain on marketable securities	(6,395)	265	(5,046)	1,571
Other	(2,175)	(193)	(1,416)	46
Total other comprehensive income (loss)	5,823	7,791	(2,941)	6,596	$ (6,538)
Comprehensive income	156,173	146,357	268,216	266,436
Comprehensive income attributable to noncontrolling interest	529	168	894	395
Comprehensive income attributable to common stockholders	$ 155,644	$ 146,189	$ 267,322	$ 266,041