SIGNIFICANT TRANSACTIONS - Additional Information (Details) - USD ($) $ in Thousands			3 Months Ended								12 Months Ended
	Oct. 30, 2020	Oct. 01, 2020	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jun. 03, 2019
Business Combination Segment Allocation [Line Items]
Reduction in non-recourse funding obligations			$ (2,197)				$ (3,082,753)				$ (2,197)	$ (3,082,753)
Reduction in income before taxes			(43,598)	$ (72,612)	$ (205,841)	$ (91,473)	(81,157)	$ (239,841)	$ (185,723)	$ (176,727)	(413,524)	(683,448)	$ (247,588)
Reduction to net investment income			(651,377)	(738,171)	(740,435)	(752,980)	(752,503)	(739,711)	(685,194)	(641,422)	(2,882,963)	(2,818,830)	(2,338,902)
Decrease in other ceded operating expenses											(774,889)	(773,665)	(774,110)
Fixed maturities, held-to-maturity							2,823,881					2,823,881
Excess of loss reinsurance asset, amount backing economic reserve liability			4,580,000								4,580,000
Other income			$ 184,172	$ 115,484	$ 111,364	$ 127,170	$ 119,168	$ 115,679	$ 104,172	$ 78,136	$ 538,190	$ 417,155	$ 321,019
Golden Gate
Business Combination Segment Allocation [Line Items]
Merger agreement term		20 years
Merger agreement extension term		25 years
Maximum commitment amount		$ 5,000,000
Individual Life Business
Business Combination Segment Allocation [Line Items]
Coinsurance basis percentage														100.00%
Ceded commissions for reinsurance														$ 765,700
Other income	$ 94,400
Cash settlement	24,100
Reserve adjustments	$ 70,300
Golden Gate, Captive Merger
Business Combination Segment Allocation [Line Items]
Reduction in fixed maturities at amortized cost		1,858,000
Reduction in non-recourse funding obligations		1,858,000
Reduction in income before taxes		54,100
Payments to settle outstanding principal with third parties		329,900
Payments to settle outstanding principal with third parties, amount held by external parties		20,600
Golden Gate, Captive Merger | Nonconsolidated Affiliates
Business Combination Segment Allocation [Line Items]
Payments to settle outstanding principal with third parties		309,300
Golden Gate, Captive Merger | PLC
Business Combination Segment Allocation [Line Items]
Payments to settle merger obligations		134,800
Golden Gate V and Red Mountain
Business Combination Segment Allocation [Line Items]
Reduction in non-recourse funding obligations		(806,000)
Reduction in income before taxes		(16,300)
Reduction to net investment income		72,300
Decrease in other ceded operating expenses		56,000
Fixed maturities, held-to-maturity		$ 822,300