Consolidated Statements Of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Net income	$ 135,814	$ 68,409	$ 49,879
Other comprehensive income, net of tax:
Foreign currency translation adjustments	239	(3,138)	805
Unrealized gains/(losses) on investments:
Unrealized holding losses arising during the period	(17)	(809)	(3,056)
Net (gains)/losses reclassified into earnings	(28)	6,497	271
Net unrealized gains/(losses) on investments	(45)	5,688	(2,785)
Unrealized gains/(losses) on hedging securities:
Unrealized hedge gains/(losses) arising during the period	1,444	4,046	(2,563)
Net unrealized gains/(losses) on hedging securities	4,304	(476)	(3,665)
Other comprehensive income	4,498	2,074	(5,645)
Comprehensive income	140,312	70,483	44,234
Revenue Hedges [Member]
Unrealized gains/(losses) on hedging securities:
Net (gains)/losses reclassified into earnings	7,113	(6,223)	(6,421)
Expense Hedges [Member]
Unrealized gains/(losses) on hedging securities:
Net (gains)/losses reclassified into earnings	$ (4,253)	$ 1,701	$ 5,319