CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 235,473	$ 120,040	$ 358,770	$ (57,783)
Other comprehensive income (loss), net of tax:
Unrealized gains (losses) arising during the period, net of reclassification adjustment	7,974	367,684	(192,809)	113,780
Foreign currency translation adjustment	3,482	3,834	4,731	(3,891)
Total other comprehensive income (loss), net of tax	11,456	371,518	(188,078)	109,889
Comprehensive income	246,929	491,558	170,692	52,106
Unrealized gains (losses) on available for sale investments, net of tax:
Other comprehensive income (loss), net of tax:
Adjustment for reclassification of net realized (gains) losses and impairment losses recognized in net income (loss)	(42,720)	(6,816)	(71,601)	(1,159)
Unrealized gains (losses) arising during the period, net of reclassification adjustment	7,974	367,684	(192,809)	113,780
Unrealized gains (losses) on available for sale investments, net of tax: | 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 holding gain (loss) arising during period	50,873	371,288	(120,971)	117,968
Unrealized gains (losses) on available for sale investments, net of tax: | 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 holding gain (loss) arising during period	$ (179)	$ 3,212	$ (237)	$ (3,029)