SHAREHOLDERS' EQUITY - Reclassifications Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Sales and redemptions										$ 28	$ 141	$ 302
Other-than-temporary impairment losses realized										(37)	(85)	(154)
Total before tax		$ 999	$ 1,075	$ 1,045	$ 898	$ 1,153	$ 963	$ 834	$ 1,117	4,018	4,067	3,862
Income Tax (Expense) Benefit		$ 1,585	$ (359)	$ (332)	$ (306)	$ (402)	$ (334)	$ (286)	$ (386)	586	(1,408)	(1,329)
Net of tax										$ 4,604	$ 2,659	$ 2,533
The expected U.S. tax rate										35.00%	35.00%	35.00%
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net of tax										$ (12)	$ 32	$ 40
Reclassification out of Accumulated Other Comprehensive Income | Unrealized gains (losses) on investment securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Sales and redemptions										27	136	214
Other-than-temporary impairment losses realized										(29)	(83)	(153)
Total before tax										(2)	53	61
Income Tax (Expense) Benefit	[1]									1	(18)	(21)
Net of tax										(1)	35	40
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)	[2]									(17)	(15)	(17)
Acquisition and operating expenses, prior service (cost) credit	[2]									0	11	17
Income Tax (Expense) Benefit	[1]									6	1	0
Net of tax										$ (11)	$ (3)	$ 0

[1] Based on 35% tax rate

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