OTHER COMPREHENSIVE INCOME (LOSS) (Reclassifications Out of AOCI Into Net Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Reclassification out of accumulated comprehensive income into net income available to common shareholders [Line Items]
Other realized gains (losses)	$ 39,394	$ 22,059	$ (2,272)	$ 38,866
Impairment losses	(112)	0	(1,302)	0
OTTI losses	0	(834)	0	(4,870)
Income (loss) before income taxes and interest in income (loss) of equity method investments	123,831	188,877	(35,282)	296,678
Income tax (expense) benefit	(10,893)	(14,469)	(6,026)	(15,703)
Net income (loss) available (attributable) to common shareholders	112,477	166,387	(72,908)	264,515
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)	9,722	8,975	6,786	(863)
Impairment losses	(112)	0	(1,302)	0
OTTI losses	0	(834)	0	(4,870)
Income (loss) before income taxes and interest in income (loss) of equity method investments	9,610	8,141	5,484	(5,733)
Income tax (expense) benefit	(2,794)	(1,192)	(4,325)	(652)
Net income (loss) available (attributable) to common shareholders	$ 6,816	$ 6,949	$ 1,159	$ (6,385)