Stockholders' Equity (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Other comprehensive income
Net change in unrealized gains (losses) related to marketable securities, Before-Tax Amount	$ (8,285)	$ (5,169)	$ 2,789	$ (8,493)
Net change in unrealized gains (losses) related to marketable securities, Tax (Expense) Benefit	3,231	2,029	(1,088)	2,702
Net change in unrealized gains (losses) on marketable securities, Net-of-Tax Amount	(5,054)	(3,140)	1,701	(5,791)
Reclassification adjustment for amounts included in net income, Before-Tax Amount	(297)	(382)	(294)	(581)
Reclassification adjustment for amounts included in net income, Tax (Expense) Benefit	116	146	115	186
Reclassification adjustments for amounts included in net income, Net-of-Tax Amount	(181)	(236)	(179)	(395)
Foreign currency translation adjustment, Before-Tax Amount	(96)	369	58	456
Foreign currency translation adjustment, Tax (Expense) Benefit
Foreign currency translation adjustment, Net-of-Tax Amount	(96)	369	58	456
Total Other Comprehensive Income (Loss), Before-Tax Amount	(8,678)	(5,182)	2,553	(8,618)
Total Other Comprehensive Income (Loss), Tax (Expense) Benefit	3,347	2,175	(973)	2,888
Other Comprehensive Income (Loss), net of tax	$ (5,331)	$ (3,007)	$ 1,580	$ (5,730)