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
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 94,748	$ 178,186	$ 456,071	$ 564,816
Foreign currency forward exchange contracts:
Unrealized holding gain (loss)	1,615	1,118	(4,901)	4,024
Reclassification adjustment for loss included in net income	3,622	1,868	1,918	3,445
Investments in marketable securities:
Unrealized holding (loss) gain	(2)	29	7	18
Reclassification adjustment for loss (gain) included in net income	(14)	(28)	(146)	56
Total other comprehensive gain (loss)	5,221	2,987	(3,122)	7,543
Comprehensive income	$ 99,969	$ 181,173	$ 452,949	$ 572,359