CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 149,034	$ 120,759	$ 419,222
Other comprehensive loss:
Foreign currency translation	(10,668)	(10,872)
Change in unrealized gain on marketable securities	181	1,349
Other	(1,880)	759
Total other comprehensive loss	(12,367)	(8,764)	$ (20,686)
Comprehensive income	136,667	111,995
Comprehensive income attributable to noncontrolling interest	54	317
Comprehensive income attributable to common stockholders	$ 136,613	$ 111,678