OTHER COMPREHENSIVE INCOME (LOSS) (Reclassifications Out of AOCI Into Net Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Reclassification out of accumulated comprehensive income into net income available to common shareholders [Line Items]
Other realized investment gains (losses)	$ 15,985	$ (12,082)	$ 54,850	$ (69,917)
OTTI losses	(1,458)	(5,546)	(6,328)	(7,634)
Income before income taxes and interest in income of equity method investments	45,756	48,903	342,432	222,202
Income tax (expense) benefit	(8,147)	3,525	(23,850)	3,565
Net income available to common shareholders	27,745	43,439	292,258	198,843
Unrealized investment gains (losses) 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 investment gains (losses)	17,904	(21,350)	17,041	(71,918)
OTTI losses	(1,458)	(5,546)	(6,328)	(7,634)
Income before income taxes and interest in income of equity method investments	16,446	(26,896)	10,713	(79,552)
Income tax (expense) benefit	(1,638)	972	(2,290)	2,363
Net income available to common shareholders	$ 14,808	$ (25,924)	$ 8,423	$ (77,189)