Other Comprehensive Income - Tax effects on components of other comprehensive income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Before tax amount:
Unrealized holding gains (losses) arising during period, before tax	$ (406,774)	$ 754,572	$ 562,576
Less reclassification of net realized gains (losses) included in net income, before tax	154,996	474,529	127,878
Foreign currency translation adjustments, before tax	(64,423)	33,706	18,463
Other comprehensive income (loss), before tax	(626,193)	313,749	453,161
Tax expense (benefit):
Unrealized holding gains (losses) arising during period, tax	(19,845)	75,855	61,805
Less reclassification of net realized gains (losses) included in net income, tax	38,928	48,342	8,937
Foreign currency translation adjustments, tax	59	370	353
Other comprehensive income (loss), tax	(58,714)	27,883	53,221
Net of tax amount:
Unrealized holding gains (losses) arising during period, net of tax	(386,929)	678,717	500,771
Less reclassification of net realized gains (losses) included in net income, net of tax	116,068	426,187	118,941
Foreign currency translation adjustments, net of tax	(64,482)	33,336	18,110
Net current period other comprehensive income (loss)	$ (567,479)	$ 285,866	$ 399,940