INVESTMENT OPERATIONS - Schedule of Amortized Cost and Fair Value of the Company's Investments Classified as Available-for-Sale (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Schedule of Investments [Line Items]
Amortized Cost	$ 64,222	$ 63,220
Gross Unrealized Gains	3,957	7,053
Gross Unrealized Losses	(465)	(131)
Allowance for Expected Credit Losses	(4)	(23)
Fair Value	67,710	70,119
Residential mortgage-backed securities
Schedule of Investments [Line Items]
Amortized Cost	6,872	6,510
Gross Unrealized Gains	89	159
Gross Unrealized Losses	(58)	(1)
Allowance for Expected Credit Losses	0	0
Fair Value	6,903	6,668
Commercial mortgage-backed securities
Schedule of Investments [Line Items]
Amortized Cost	2,346	2,429
Gross Unrealized Gains	92	128
Gross Unrealized Losses	(11)	(19)
Allowance for Expected Credit Losses	(2)	(4)
Fair Value	2,425	2,534
Other asset-backed securities
Schedule of Investments [Line Items]
Amortized Cost	1,505	1,546
Gross Unrealized Gains	36	40
Gross Unrealized Losses	(4)	(7)
Allowance for Expected Credit Losses	(1)	(1)
Fair Value	1,536	1,578
U.S. government-related securities
Schedule of Investments [Line Items]
Amortized Cost	980	1,492
Gross Unrealized Gains	17	26
Gross Unrealized Losses	(37)	(3)
Allowance for Expected Credit Losses	0	0
Fair Value	960	1,515
Other government-related securities
Schedule of Investments [Line Items]
Amortized Cost	591	622
Gross Unrealized Gains	54	96
Gross Unrealized Losses	(3)	(1)
Allowance for Expected Credit Losses	0	0
Fair Value	642	717
States, municipals, and political subdivisions
Schedule of Investments [Line Items]
Amortized Cost	3,821	3,902
Gross Unrealized Gains	301	519
Gross Unrealized Losses	(3)	(1)
Allowance for Expected Credit Losses	0	0
Fair Value	4,119	4,420
Corporate securities
Schedule of Investments [Line Items]
Amortized Cost	47,342	46,150
Gross Unrealized Gains	3,364	6,074
Gross Unrealized Losses	(348)	(99)
Allowance for Expected Credit Losses	(1)	(18)	$ (52)	$ 0
Fair Value	50,357	52,107
Redeemable preferred stocks
Schedule of Investments [Line Items]
Amortized Cost	213	183
Gross Unrealized Gains	4	11
Gross Unrealized Losses	(1)	0
Allowance for Expected Credit Losses	0	0
Fair Value	216	194
Fixed maturities
Schedule of Investments [Line Items]
Amortized Cost	63,670	62,834
Gross Unrealized Gains	3,957	7,053
Gross Unrealized Losses	(465)	(131)
Allowance for Expected Credit Losses	(4)	(23)	$ (52)	$ 0
Fair Value	67,158	69,733
Short-term investments
Schedule of Investments [Line Items]
Amortized Cost	552	386
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Allowance for Expected Credit Losses	0	0
Fair Value	$ 552	$ 386