OTHER COMPREHENSIVE INCOME (LOSS) (Reclassifications Out of AOCI Into Net Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Reclassification out of accumulated comprehensive income into net income available to common shareholders [Line Items]
Other realized gains (losses)	$ 52,034	$ 15,985	$ 49,761	$ 54,850
Impairment losses	(184)	0	(1,486)	0
OTTI losses	0	(1,458)	0	(6,328)
Income (loss) before income taxes and interest in income (loss) of equity method investments	(80,334)	45,756	(115,618)	342,432
Income tax (expense) benefit	12,056	(8,147)	6,030	(23,850)
Net income (loss) available (attributable) to common shareholders	(72,945)	27,745	(145,855)	292,258
Unrealized gains on available for sale investments | Reclassification out of Accumulated Other Comprehensive Income
Reclassification out of accumulated comprehensive income into net income available to common shareholders [Line Items]
Other realized gains (losses)	33,284	17,904	40,070	17,041
Impairment losses	(184)		(1,486)	0
OTTI losses	0	(1,458)	0	(6,328)
Income (loss) before income taxes and interest in income (loss) of equity method investments	33,100	16,446	38,584	10,713
Income tax (expense) benefit	(3,970)	(1,638)	(8,295)	(2,290)
Net income (loss) available (attributable) to common shareholders	$ 29,130	$ 14,808	$ 30,289	$ 8,423