CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
Net income, as reported	$ 338,661	$ 340,020	$ 286,219
Other comprehensive (loss) income:
Change in foreign currency translation	(1,782)	2,096	(3,306)
Available-for-sale investments:
Change in net unrealized gains		1,525	1,478
Reclassification adjustment for net gains included in net income	(1,525)
Net change in available-for-sale investments	(1,525)	1,525	1,478
Other comprehensive (loss) income	(3,307)	3,621	(1,828)
Comprehensive income	$ 335,354	$ 343,641	$ 284,391