Other Comprehensive Income (Loss) - Components of other comprehensive income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Before tax amount:
Unrealized holding gains (losses) arising during period, before tax	$ (784,890)	$ (294,360)
Less reclassification of net realized gains included in net income, before tax	(120,362)	357
Foreign currency translation adjustments, before tax	(2,565)	(28,415)
Other comprehensive income (loss), before tax	(667,093)	(323,132)
Tax expense (benefit):
Unrealized holding gains (losses) arising during period, tax	(100,535)	(32,610)
Less reclassification of net realized gains included in net income, tax	(18,084)	3,054
Foreign currency translation adjustments, tax	203	169
Other comprehensive income (loss), tax	(82,248)	(35,495)
Net of tax amount:
Unrealized holding gains (losses) arising during period, net of tax	(684,355)	(261,750)
Less reclassification of net realized gains included in net income, net of tax	(102,278)	(2,697)
Foreign currency translation adjustments, net of tax	(2,768)	(28,584)
Net current period other comprehensive income (loss)	$ (584,845)	$ (287,637)