Condensed Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Statement of Other Comprehensive Income [Abstract]
Net income	$ 45,599	$ 35,098	$ 133,535	$ 119,989
Unrealized investment gains (losses):
Change in unrealized gains (losses) on investment securities	24,139	(9,839)	45,584	2,604
Reclassification adjustment for realized investment (gains) losses included in net income	(3,654)	(126)	(10,115)	(2,419)
Foreign currency translation adjustments:
Change in unrealized foreign currency translation gains (losses)	7,867	(11,558)	6,998	(7,911)
Total other comprehensive income (loss) before income taxes	28,352	(21,523)	42,467	(7,726)
Income tax expense (benefit) related to items of other comprehensive income (loss)	7,260	(3,487)	12,426	(662)
Other comprehensive income (loss), net of income taxes	21,092	(18,036)	30,041	(7,064)
Total comprehensive income	$ 66,691	$ 17,062	$ 163,576	$ 112,925