OTHER COMPREHENSIVE INCOME (LOSS) (Tax Effects of Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Before tax amount
Total other comprehensive income, net of tax	$ 410,368	$ 141,322	$ 127,886	$ 364,664
Income tax (expense) benefit
Total other comprehensive income, net of tax	(38,850)	(14,273)	(17,997)	(31,409)
Net of tax amount
Total other comprehensive income, net of tax	371,518	127,049	109,889	333,255
Available for sale investments:
Before tax amount
Adjustment for reclassification of net realized (gains) losses, impairment losses and OTTI losses recognized in net income (loss)	(9,610)	(8,141)	(5,484)	5,733
Total other comprehensive income, net of tax	406,534	138,766	131,777	359,445
Income tax (expense) benefit
Adjustment for reclassification of net realized (gains) losses, impairment losses and OTTI losses recognized in net income (loss)	2,794	1,192	4,325	652
Total other comprehensive income, net of tax	(38,850)	(14,273)	(17,997)	(31,409)
Net of tax amount
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
Total other comprehensive income, net of tax	367,684	124,493	113,780	328,036
Available for sale investments: | Unrealized gains 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	412,802	146,907	140,018	353,712
Income tax (expense) benefit
Unrealized gains (losses) arising during the period	(41,514)	(15,465)	(22,050)	(32,061)
Net of tax amount
Unrealized gains (losses) arising during the period	371,288	131,442	117,968	321,651
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	3,342	0	(2,757)	0
Income tax (expense) benefit
Unrealized gains (losses) arising during the period	(130)	0	(272)	0
Net of tax amount
Unrealized gains (losses) arising during the period	3,212	0	(3,029)	0
Foreign currency translation adjustment
Before tax amount
Total other comprehensive income, net of tax	3,834	2,556	(3,891)	5,219
Income tax (expense) benefit
Total other comprehensive income, net of tax	0	0	0	0
Net of tax amount
Total other comprehensive income, net of tax	$ 3,834	$ 2,556	$ (3,891)	$ 5,219