INVESTMENT OPERATIONS - Schedule of Amortized Cost and Fair Value of the Company's Investments Classified as Available-for-Sale (Details) - USD ($) $ in Millions	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Schedule of Investments [Line Items]
Amortized Cost	$ 66,022		$ 63,220
Gross Unrealized Gains	5,522		7,053
Gross Unrealized Losses	(227)		(131)
Allowance for Expected Credit Losses	(2)		(23)
Fair Value	71,315		70,119
Residential mortgage-backed securities
Schedule of Investments [Line Items]
Amortized Cost	7,345		6,510
Gross Unrealized Gains	59		159
Gross Unrealized Losses	(58)		(1)
Allowance for Expected Credit Losses	0		0
Fair Value	7,346		6,668
Commercial mortgage-backed securities
Schedule of Investments [Line Items]
Amortized Cost	2,196		2,429
Gross Unrealized Gains	98		128
Gross Unrealized Losses	(6)		(19)
Allowance for Expected Credit Losses	(1)	$ (1)	(4)	$ 0	$ 0	$ 0
Fair Value	2,287		2,534
Other asset-backed securities
Schedule of Investments [Line Items]
Amortized Cost	1,438		1,546
Gross Unrealized Gains	39		40
Gross Unrealized Losses	(1)		(7)
Allowance for Expected Credit Losses	0		(1)
Fair Value	1,476		1,578
U.S. government-related securities
Schedule of Investments [Line Items]
Amortized Cost	821		1,492
Gross Unrealized Gains	15		26
Gross Unrealized Losses	(24)		(3)
Allowance for Expected Credit Losses	0		0
Fair Value	812		1,515
Other government-related securities
Schedule of Investments [Line Items]
Amortized Cost	688		622
Gross Unrealized Gains	76		96
Gross Unrealized Losses	(2)		(1)
Allowance for Expected Credit Losses	0		0
Fair Value	762		717
States, municipals, and political subdivisions
Schedule of Investments [Line Items]
Amortized Cost	3,760		3,902
Gross Unrealized Gains	414		519
Gross Unrealized Losses	(1)		(1)
Allowance for Expected Credit Losses	0		0
Fair Value	4,173		4,420
Corporate securities
Schedule of Investments [Line Items]
Amortized Cost	48,935		46,150
Gross Unrealized Gains	4,808		6,074
Gross Unrealized Losses	(135)		(99)
Allowance for Expected Credit Losses	(1)	(1)	(18)	(18)	(81)	0
Fair Value	53,607		52,107
Redeemable preferred stocks
Schedule of Investments [Line Items]
Amortized Cost	297		183
Gross Unrealized Gains	13		11
Gross Unrealized Losses	0		0
Allowance for Expected Credit Losses	0		0
Fair Value	310		194
Fixed maturities
Schedule of Investments [Line Items]
Amortized Cost	65,480		62,834
Gross Unrealized Gains	5,522		7,053
Gross Unrealized Losses	(227)		(131)
Allowance for Expected Credit Losses	(2)	$ (2)	(23)	$ (19)	$ (82)	$ 0
Fair Value	70,773		69,733
Short-term investments
Schedule of Investments [Line Items]
Amortized Cost	542		386
Gross Unrealized Gains	0		0
Gross Unrealized Losses	0		0
Allowance for Expected Credit Losses	0		0
Fair Value	$ 542		$ 386