CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 150,674	$ 34,778	$ 330,773	$ 183,982
Other comprehensive income (loss), net of tax:
Unrealized gains (losses) arising during the period, net of reclassification adjustment	(61,796)	(379,621)	127,143	(777,232)
Foreign currency translation adjustment	3,183	(6,193)	2,648	(3,418)
Total other comprehensive income (loss), net of tax	(58,613)	(385,814)	129,791	(780,650)
Comprehensive income (loss)	92,061	(351,036)	460,564	(596,668)
Unrealized gains (losses) on available for sale investments
Other comprehensive income (loss), net of tax:
Adjustment for reclassification of net realized (gains) losses and impairment losses recognized in net income (loss)	36,621	84,364	77,370	129,706
Unrealized gains (losses) arising during the period, net of reclassification adjustment	(61,796)	(379,621)	127,143	(777,232)
Unrealized gains (losses) on available for sale investments | Unrealized gains (losses) arising during the period for which an allowance for expected credit losses has not been recognized
Other comprehensive income (loss), net of tax:
Unrealized gains (losses) arising during period	(98,402)	(461,946)	41,700	(901,771)
Unrealized gains (losses) on available for sale investments | Unrealized gains (losses) arising during the period for which an allowance for expected credit losses has been recognized
Other comprehensive income (loss), net of tax:
Unrealized gains (losses) arising during period	$ (15)	$ (2,039)	$ 8,073	$ (5,167)