Accumulated Other Comprehensive Income - Reclassifications Out of AOCI (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income	[1]	$ 51	$ (88)
Income (loss) from continuing operations before income taxes		772	176
Income taxes		147	23
Interest income — Loans		889	1,026
Interest expense — Long-term debt		(60)	(90)
Investment banking and debt placement fees		162	116
Other expense		624	515
INCOME (LOSS) FROM CONTINUING OPERATIONS		618	145
Reclassification out of Accumulated Other Comprehensive Income | Realized gains on available for sale securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income		0	4
Reclassification out of Accumulated Other Comprehensive Income | Unrealized gains (losses) on securities available for sale
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income (loss) from continuing operations before income taxes		0	4
Income taxes		0	1
INCOME (LOSS) FROM CONTINUING OPERATIONS		0	3
Reclassification out of Accumulated Other Comprehensive Income | Unrealized gains (losses) on derivative financial instruments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income (loss) from continuing operations before income taxes		89	33
Income taxes		21	8
Investment banking and debt placement fees		1	0
INCOME (LOSS) FROM CONTINUING OPERATIONS		68	25
Reclassification out of Accumulated Other Comprehensive Income | Amortization of losses
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other expense		(5)	(4)
Reclassification out of Accumulated Other Comprehensive Income | Settlement loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other expense		0	(4)
Reclassification out of Accumulated Other Comprehensive Income | Net pension and postretirement benefit costs
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income (loss) from continuing operations before income taxes		(5)	(8)
Income taxes		(1)	(2)
INCOME (LOSS) FROM CONTINUING OPERATIONS		(4)	(6)
Interest income – loans | Reclassification out of Accumulated Other Comprehensive Income | Unrealized gains (losses) on derivative financial instruments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income — Loans		89	34
Interest expense — Long-term debt | Reclassification out of Accumulated Other Comprehensive Income | Unrealized gains (losses) on derivative financial instruments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense — Long-term debt		$ (1)	$ (1)

[1] For the three months ended March 31, 2021, net securities gains (losses) totaled less than $1 million for the three months ended March 31, 2020, net securities gains (losses) totaled $4 million. For the three months ended March 31, 2021, and March 31, 2020, we did not have any impairment losses related to securities.