OTHER COMPREHENSIVE INCOME (LOSS) (Tax Effects of Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Before tax amount
Total other comprehensive income (loss), net of tax	$ 24,883	$ (78)	$ 389,548	$ (193,429)
Tax (expense) benefit
Total other comprehensive income (loss), net of tax	(4,732)	935	(36,142)	6,233
Net of tax amount
Total other comprehensive income (loss), net of tax	20,151	857	353,406	(187,196)
Available for sale investments:
Before tax amount
Unrealized investment gains (losses) arising during the period	45,939	(27,968)	399,652	(266,117)
Adjustment for reclassification of net realized investment (gains) losses and OTTI losses recognized in net income	(16,446)	26,896	(10,713)	79,552
Total other comprehensive income (loss), net of tax	29,493	(1,072)	388,939	(186,565)
Tax (expense) benefit
Unrealized investment gains (losses) arising during the period	(6,370)	1,907	(38,432)	8,596
Adjustment for reclassification of net realized investment (gains) losses and OTTI losses recognized in net income	1,638	(972)	2,290	(2,363)
Total other comprehensive income (loss), net of tax	(4,732)	935	(36,142)	6,233
Net of tax amount
Unrealized investment gains (losses) arising during the period	39,569	(26,061)	361,220	(257,521)
Adjustment for reclassification of net realized investment (gains) losses and OTTI losses recognized in net income	(14,808)	25,924	(8,423)	77,189
Total other comprehensive income (loss), net of tax	24,761	(137)	352,797	(180,332)
Non-credit portion of OTTI losses
Before tax amount
Total other comprehensive income (loss), net of tax	0	0	0	0
Tax (expense) benefit
Total other comprehensive income (loss), net of tax	0	0	0	0
Net of tax amount
Total other comprehensive income (loss), net of tax	0	0	0	0
Foreign currency translation adjustment
Before tax amount
Total other comprehensive income (loss), net of tax	(4,610)	994	609	(6,864)
Tax (expense) benefit
Total other comprehensive income (loss), net of tax	0	0	0	0
Net of tax amount
Total other comprehensive income (loss), net of tax	$ (4,610)	$ 994	$ 609	$ (6,864)