OTHER COMPREHENSIVE INCOME (LOSS) (Tax Effects of Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Before tax amount
Total other comprehensive income, net of tax	$ 75,360	$ 24,883	$ 203,247	$ 389,548
Income tax (expense) benefit
Total other comprehensive income, net of tax	(6,848)	(4,732)	(24,846)	(36,142)
Net of tax amount
Total other comprehensive income, net of tax	68,512	20,151	178,401	353,406
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)	(33,100)	(16,446)	(38,584)	(10,713)
Total other comprehensive income, net of tax	73,050	29,493	204,828	388,939
Income tax (expense) benefit
Adjustment for reclassification of net realized (gains) losses, impairment losses and OTTI losses recognized in net income (loss)	3,970	1,638	8,295	2,290
Total other comprehensive income, net of tax	(6,848)	(4,732)	(24,846)	(36,142)
Net of tax amount
Adjustment for reclassification of net realized (gains) losses, impairment losses and OTTI losses recognized in net income (loss)	(29,130)	(14,808)	(30,289)	(8,423)
Total other comprehensive income, net of tax	66,202	24,761	179,982	352,797
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	105,932	45,939	243,522	399,652
Income tax (expense) benefit
Unrealized gains (losses) arising during the period	(10,820)	(6,370)	(33,139)	(38,432)
Net of tax amount
Unrealized gains (losses) arising during the period	95,112	39,569	210,383	361,220
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	218	0	(110)	0
Income tax (expense) benefit
Unrealized gains (losses) arising during the period	2	0	(2)	0
Net of tax amount
Unrealized gains (losses) arising during the period	220	0	(112)	0
Foreign currency translation adjustment
Before tax amount
Total other comprehensive income, net of tax	2,310	(4,610)	(1,581)	609
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	$ 2,310	$ (4,610)	$ (1,581)	$ 609