SHAREHOLDERS' EQUITY - Reclassifications Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2019		Mar. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other-than-temporary impairment losses realized		$ (2)		$ (7)
Other gains (losses)		73		(127)
Total before tax		1,242		982
Income tax (expense) or benefit		(314)		(265)
Net of tax		$ 928		$ 717
Blended statutory income tax rate		25.00%		27.00%
Reclassification Out Of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net of tax		$ 10		$ (2)
Reclassification Out Of Accumulated Other Comprehensive Income | Unrealized gains (losses) on investment securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other-than-temporary impairment losses realized		0		0
Other gains (losses)		17		2
Total before tax		17		2
Income tax (expense) or benefit		(4)	[1]	(1)	[2]
Net of tax		13		1
Reclassification Out Of Accumulated Other Comprehensive Income | Pension liability adjustment
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Acquisition and operating expenses, actuarial gains (losses)	[3]	(4)		(4)
Acquisition and operating expenses, prior service (cost) credit	[3]	0		0
Income tax (expense) or benefit		1	[1]	1	[2]
Net of tax		$ (3)		$ (3)

[1] Based on 25% blended tax rate

[2] Based on 27% blended tax rate

[3] These accumulated other comprehensive income components are included in the computation of net periodic pension cost (see Note 11 for additional details).