CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 618,609	$ (120,424)	$ 323,473
Other comprehensive income (loss), net of tax:
Unrealized gains (losses) arising during the year, net of reclassification adjustment	(358,480)	239,114	349,886
Foreign currency translation adjustment	621	3,571	(1,066)
Total other comprehensive income (loss), net of tax	(357,859)	242,685	348,820
Comprehensive income	260,750	122,261	672,293
Unrealized gains (losses) on available for sale investments
Other comprehensive income (loss), net of tax:
Adjustment for reclassification of net realized (gains) losses, impairment losses and OTTI losses recognized in net income (loss)	(87,114)	(78,012)	(24,729)
Unrealized gains (losses) arising during the year, net of reclassification adjustment	(358,480)	239,114	349,886
Unrealized gains (losses) arising during the year for which an allowance for expected credit losses has not been recognized | Unrealized gains (losses) on available for sale investments
Other comprehensive income (loss), net of tax:
Unrealized gains (losses) arising during the year	(271,447)	317,166	374,615
Unrealized gains (losses) arising during the year for which an allowance for expected credit losses has been recognized | Unrealized gains (losses) on available for sale investments
Other comprehensive income (loss), net of tax:
Unrealized gains (losses) arising during the year	$ 81	$ (40)	$ 0