Other Comprehensive Income (Loss) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Other comprehensive income (loss), before-tax amount
Foreign currency translation adjustments, before-tax amount	$ 2,737	$ 3,253
Unrealized holding gains (losses) on available-for-sale securities, before tax amount	17,783	51,021
Recognition of previously unrealized (gains) losses on available-for-sale securities included in net income (loss), before tax amount	1,362	(80,887)
Other comprehensive income (loss), before-tax amount	21,882	(26,613)
Other comprehensive income (loss), tax (expense) or benefit
Unrealized holding gains (losses) on available-for-sale securities, tax (expense) benefit	(6,996)
Other Comprehensive Income (Loss), Tax	(6,996)
Other comprehensive income (loss):
Foreign currency translation adjustments, net of tax	2,737	3,253
Unrealized holding gains (losses) on available-for-sale securities, net of tax	10,787	51,021
Recognition of previously unrealized (gains) losses on available-for-sale securities included in net income (loss)	1,362	(80,887)
Total other comprehensive income (loss), net of tax	14,886	(26,613)
Accumulated other comprehensive income (loss)
Foreign currency translation adjustments, balance at beginning of period, net	(5,033)
Foreign currency translation adjustments, before-tax amount, other comprehensive income (loss) before reclassification	2,737	3,253
Foreign currency translation adjustments, balance at end of period, net	(2,296)
Unrealized / Recognized Gains (Losses), balance at beginning of period, net	193,836
Unrealized / Recognized Gains (Losses), before-tax amount, other comprehensive income (loss) before reclassification	17,783
Unrealized / Recognized Gains (Losses), before-tax amount, amounts reclassified from accumulated other comprehensive income (loss)	1,362	(80,887)
Unrealized holding gains (losses) on available-for-sale securities, tax (expense) benefit	(6,996)
Unrealized / Recognized Gains (Losses), balance at end of period, net	205,985
Accumulated other comprehensive income (loss), balance at beginning of period, net	188,803
Other comprehensive income (loss), before-tax amount, other comprehensive income (loss) before reclassification	20,520
Other comprehensive income (loss), before-tax amount, amounts reclassified from accumulated other comprehensive income (loss)	1,362
Other Comprehensive Income (Loss), tax (expense) benefit	(6,996)
Accumulated other comprehensive income (loss), balance at end of period, net	$ 203,689