Other Comprehensive Income (Loss) - Components of other comprehensive income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Before tax amount:
Unrealized holding gains arising during period, before tax	$ 10,347	$ 92,773
Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss), before tax	(2)	(8)
Less reclassification of net realized gains included in net income, before tax	42,119	30,759
Foreign currency translation adjustments, before tax	(28,222)	13,869
Other comprehensive income (loss), before tax	(59,996)	75,875
Tax expense (benefit):
Unrealized holding gains arising during period, tax	876	(2,090)
Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss), tax	0	0
Less reclassification of net realized gains included in net income, tax	3,418	3,248
Foreign currency translation adjustments, tax	0	668
Other comprehensive income (loss), tax	(2,542)	(4,670)
Net of tax amount:
Unrealized holding gains arising during period, net of tax	9,471	94,863
Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss), net of tax	(2)	(8)
Less reclassification of net realized gains included in net income, net of tax	38,701	27,511
Foreign currency translation adjustments, net of tax	(28,222)	13,201
Net current period other comprehensive income (loss)	$ (57,454)	$ 80,545