OTHER COMPREHENSIVE INCOME (LOSS) (Tax Effects of Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Before tax amount
Total comprehensive income, net of tax	$ 13,293	$ 410,368	$ (212,353)	$ 127,886
Income tax (expense) benefit
Total comprehensive income, net of tax	(1,837)	(38,850)	24,275	(17,997)
Net of tax amount
Total comprehensive income, net of tax	11,456	371,518	(188,078)	109,889
Available for sale investments:
Before tax amount
Adjustment for reclassification of net realized (gains) losses and impairment losses recognized in net income (loss)	(46,704)	(9,610)	(77,579)	(5,484)
Total comprehensive income, net of tax	9,811	406,534	(217,084)	131,777
Income tax (expense) benefit
Adjustment for reclassification of net realized (gains) losses and impairment losses recognized in net income (loss)	3,984	2,794	5,978	4,325
Total comprehensive income, net of tax	(1,837)	(38,850)	24,275	(17,997)
Net of tax amount
Adjustment for reclassification of net realized (gains) losses and impairment losses recognized in net income (loss)	(42,720)	(6,816)	(71,601)	(1,159)
Total comprehensive income, net of tax	7,974	367,684	(192,809)	113,780
Available for sale investments: | Unrealized gains (losses) arising during the period for which an allowance for expected credit losses has not been recognized
Before tax amount
Unrealized gains (losses) arising during the period	56,694	412,802	(139,268)	140,018
Income tax (expense) benefit
Unrealized gains (losses) arising during the period	(5,821)	(41,514)	18,297	(22,050)
Net of tax amount
Unrealized gains (losses) arising during the period	50,873	371,288	(120,971)	117,968
Available for sale investments: | Unrealized gains (losses) arising during the period for which an allowance for expected credit losses has been recognized
Before tax amount
Unrealized gains (losses) arising during the period	(179)	3,342	(237)	(2,757)
Income tax (expense) benefit
Unrealized gains (losses) arising during the period	0	(130)	0	(272)
Net of tax amount
Unrealized gains (losses) arising during the period	(179)	3,212	(237)	(3,029)
Foreign currency translation adjustment
Before tax amount
Total comprehensive income, net of tax	3,482	3,834	4,731	(3,891)
Income tax (expense) benefit
Total comprehensive income, net of tax	0	0	0	0
Net of tax amount
Total comprehensive income, net of tax	$ 3,482	$ 3,834	$ 4,731	$ (3,891)