Condensed Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Condensed Consolidated Statements of Comprehensive Income
Net income	$ 41,317	$ 46,446	$ 94,408	$ 191,732
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustment during the period	302	732	(697)	565
Change in fair value of corporate debt securities
Unrealized holding gains (losses) on corporate debt securities arising during the period		49	(98)	134
Less: Reclassification adjustments for gains included in net income			(1,296)
Change in fair value of corporate debt securities, net		49	(1,394)	134
Other comprehensive income (loss)	302	781	(2,091)	699
Comprehensive income	$ 41,619	$ 47,227	$ 92,317	$ 192,431