Other Comprehensive Income (Loss) - Components of other comprehensive income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Before tax amount:
Unrealized holding gains (losses) arising during period, before tax	$ (676,048)	$ 91,057	$ (1,460,938)	$ (203,303)
Less reclassification of net realized gains included in net income, before tax	(67,016)	65,810	(187,378)	66,167
Foreign currency translation adjustments, before tax	(68,562)	6,392	(71,127)	(22,023)
Other comprehensive income (loss), before tax	(677,594)	31,639	(1,344,687)	(291,493)
Tax expense (benefit):
Unrealized holding gains (losses) arising during period, tax	(78,043)	12,486	(178,578)	(20,124)
Less reclassification of net realized gains included in net income, tax	(9,306)	5,263	(27,390)	8,317
Foreign currency translation adjustments, tax	(37)	187	166	356
Other comprehensive income (loss), tax	(68,774)	7,410	(151,022)	(28,085)
Net of tax amount:
Unrealized holding gains (losses) arising during period, net of tax	(598,005)	78,571	(1,282,360)	(183,179)
Less reclassification of net realized gains included in net income, net of tax	(57,710)	60,547	(159,988)	57,850
Foreign currency translation adjustments, net of tax	(68,525)	6,205	(71,293)	(22,379)
Net current period other comprehensive income (loss)	$ (608,820)	$ 24,229	$ (1,193,665)	$ (263,408)