Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Consolidated Statements of Comprehensive Income [Abstract]
Net income (loss)	$ 54,113	$ 45,067	$ 89,904	$ 88,044
Net unrealized gain (loss) on derivative instruments arising during the period, net of tax	25,773	17,057	22,506	(1,217)
Less: Reclassification adjustment for gain (loss) on derivative instruments included in net income, net of tax	1,834	(3,650)	4,666	155
Net unrealized gain (loss) on derivative instruments qualifying as hedges	23,939	20,707	17,840	(1,372)
Foreign currency translation adjustment, net of tax	(579)	50	(435)	262
Net unrealized gain (loss) on available-for-sale investments, net of tax	(5)	87	21	103
Other comprehensive income (loss)	23,355	20,844	17,426	(1,007)
Comprehensive income (loss)	77,468	65,911	107,330	87,037
Other comprehensive income (loss), Parenthetical [Abstract]
Net unrealized gain (loss) on derivative instruments arising during the period, tax	15,059	10,576	13,129	(388)
Reclassification adjustment for gain (loss) on derivative instruments included in net income, tax	1,077	(2,191)	2,738	91
Foreign currency translation adjustment, tax	(402)	32	(265)	170
Net unrealized gains (loss) on available-for-sale investments, tax	$ (3)	$ 47	$ 11	$ 55