Other Comprehensive Income (Loss) - Components of other comprehensive income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Before tax amount:
Unrealized holding gains arising during period, before tax	$ 75,400	$ 10,347
Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss), before tax	0	(2)
Less reclassification of net realized gains included in net income, before tax	23,067	42,119
Foreign currency translation adjustments, before tax	(1,349)	(28,222)
Other comprehensive income (loss), before tax	50,984	(59,996)
Tax expense (benefit):
Unrealized holding gains arising during period, tax	4,047	876
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	1,818	3,418
Foreign currency translation adjustments, tax	0	0
Other comprehensive income (loss), tax	2,229	(2,542)
Net of tax amount:
Unrealized holding gains arising during period, net of tax	71,353	9,471
Portion of other-than-temporary impairment losses recognized in other comprehensive income (loss), net of tax	0	(2)
Less reclassification of net realized gains included in net income, net of tax	21,249	38,701
Foreign currency translation adjustments, net of tax	(1,349)	(28,222)
Net current period other comprehensive income (loss)	$ 48,755	$ (57,454)