SHAREHOLDERS' EQUITY - Reclassifications Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		1 Months Ended	3 Months Ended								12 Months Ended
		Jan. 31, 2018	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		Dec. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net investment gains (losses)											$ 159		$ (18)		$ 46
Income tax (expense) benefit			$ (265)	$ 1,303	$ (265)	$ (154)	$ (276)	$ (259)	$ (292)	$ (314)	619		(1,141)		(1,063)
Net of tax											$ 4,778		$ 3,304		$ 2,920
U.S. federal statutory corporate income tax rate		21.00%									21.00%		21.00%		21.00%		35.00%
Blended statutory income tax rate													26.00%		27.00%
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net of tax											$ (149)		$ 2		$ (47)
Reclassification out of Accumulated Other Comprehensive Income | Unrealized gains (losses) on available-for-sale securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net investment gains (losses)											(159)		18		(46)
Income tax (expense) benefit											33	[1]	(5)	[2]	12	[3]
Net of tax											(126)		13		(34)
Reclassification out of Accumulated Other Comprehensive Income | Pension liability adjustment
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Acquisition and operating expense, actuarial gains (losses)	[4]										(32)		(15)		(18)
Acquisition and operating expenses, prior service (cost) credit	[4]										3		0		0
Income tax (expense) benefit											6	[1]	4	[2]	5	[3]
Net of tax											$ (23)		$ (11)		$ (13)

[1] Based on 21% tax rate

[2] Based on 26% blended tax rate

[3] Based on 27% blended tax rate

[4] These accumulated other comprehensive income components are included in the computation of net periodic pension cost (see Note 14 for additional details).