CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 120,040	$ 177,043	$ (57,783)	$ 285,828
Other comprehensive income, net of tax:
Unrealized gains arising during the period, net of reclassification adjustment	367,684	124,493	113,780	328,036
Foreign currency translation adjustment	3,834	2,556	(3,891)	5,219
Total other comprehensive income, net of tax	371,518	127,049	109,889	333,255
Comprehensive income	491,558	304,092	52,106	619,083
Unrealized gains (losses) on available for sale investments, net of tax:
Other comprehensive income, net of tax:
Adjustment for reclassification of net realized (gains) losses, impairment losses and OTTI losses recognized in net income (loss)	(6,816)	(6,949)	(1,159)	6,385
Unrealized gains arising during the period, net of reclassification adjustment	367,684	124,493	113,780	328,036
Unrealized gains (losses) on available for sale investments, net of tax: | Unrealized gains arising during the period for which an allowance for expected credit losses has not been recognized
Other comprehensive income, net of tax:
Unrealized holding gain (loss) arising during period	371,288	131,442	117,968	321,651
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, net of tax:
Unrealized holding gain (loss) arising during period	$ 3,212	$ 0	$ (3,029)	$ 0