Other Comprehensive Income - Tax effects on components of other comprehensive income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Before tax amount:
Unrealized holding gains (losses) arising during period, before tax	$ (2,010,443)	$ (406,774)	$ 754,572
Less reclassification of net realized gains (losses) included in net income, before tax	(279,898)	154,996	474,529
Foreign currency translation adjustments, before tax	(56,554)	(64,423)	33,706
Other comprehensive income (loss), before tax	(1,787,099)	(626,193)	313,749
Tax expense (benefit):
Unrealized holding gains (losses) arising during period, tax	(237,794)	(19,845)	75,855
Less reclassification of net realized gains (losses) included in net income, tax	(32,099)	38,928	48,342
Foreign currency translation adjustments, tax	166	59	370
Other comprehensive income (loss), tax	(205,529)	(58,714)	27,883
Net of tax amount:
Unrealized holding gains (losses) arising during period, net of tax	(1,772,649)	(386,929)	678,717
Less reclassification of net realized gains (losses) included in net income, net of tax	(247,799)	116,068	426,187
Foreign currency translation adjustments, net of tax	(56,720)	(64,482)	33,336
Net current period other comprehensive income (loss)	$ (1,581,570)	$ (567,479)	$ 285,866