CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Statement of Other Comprehensive Income [Abstract]
Net income	$ 114,533	$ 73,736	$ 227,631	$ 163,828	$ 361,775
Other comprehensive income (loss):
Foreign currency translation	(2,722)	(1,607)	(4,813)	342
Change in unrealized gain on marketable debt securities	(868)	(403)	(807)	(711)
Other	1,514	(512)	2,018	(289)
Total other comprehensive loss	(2,076)	(2,522)	(3,602)	(658)	1,292
Comprehensive income	112,457	71,214	224,029	163,170
Comprehensive (loss) income attributable to noncontrolling interest	(47)	(289)	858	(823)
Comprehensive income attributable to common stockholders	$ 112,504	$ 71,503	$ 223,171	$ 163,993