OTHER COMPREHENSIVE INCOME (LOSS) (Tax Effects of Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Before tax amount
Total other comprehensive income (loss), net of tax	$ (282,482)	$ 223,342
Income tax (expense) benefit
Total other comprehensive income (loss), net of tax	20,853	(17,137)
Net of tax amount
Total other comprehensive income (loss), net of tax	(261,629)	206,205
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)	4,126	13,874
Total other comprehensive income (loss), net of tax	(274,757)	220,680
Income tax (expense) benefit
Adjustment for reclassification of net realized (gains) losses, impairment losses and OTTI losses recognized in net income (loss)	1,522	(504)
Total other comprehensive income (loss), net of tax	20,853	(17,137)
Net of tax amount
Adjustment for reclassification of net realized (gains) losses, impairment losses and OTTI losses recognized in net income (loss)	5,648	13,370
Total other comprehensive income (loss), net of tax	(253,904)	203,543
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	(260,758)	206,806
Income tax (expense) benefit
Unrealized gains (losses) arising during the period	17,796	(16,633)
Net of tax amount
Unrealized gains (losses) arising during the period	(242,962)	190,173
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	(18,125)	0
Income tax (expense) benefit
Unrealized gains (losses) arising during the period	1,535	0
Net of tax amount
Unrealized gains (losses) arising during the period	(16,590)	0
Foreign currency translation adjustment
Before tax amount
Total other comprehensive income (loss), net of tax	(7,725)	2,662
Income tax (expense) benefit
Total other comprehensive income (loss), net of tax	0	0
Net of tax amount
Total other comprehensive income (loss), net of tax	$ (7,725)	$ 2,662