Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement of Comprehensive Income [Abstract]
Net income	$ 293,487	$ 203,989	$ 200,904
Other comprehensive (loss) income:
Foreign currency translation adjustments	(4,361)	(904)	(3,553)
Change in unrealized gain on investments, net of income tax benefit (expense) of $457, $(404) and $(5,018) for the years ended December 31, 2013, 2012 and 2011, respectively	3,910	523	8,035
Other comprehensive (loss) income	(451)	(381)	4,482
Comprehensive income	$ 293,036	$ 203,608	$ 205,386