Accumulated Other Comprehensive Income - Reclassifications Out of AOCI (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income	[1]	$ 28	$ 27	$ (27)	$ 54
Income (loss) from continuing operations before income taxes		490	491	888	1,505
Income taxes		60	70	113	239
Interest income — Loans		927	1,073	2,933	3,221
Interest expense — Long-term debt		(64)	(114)	(225)	(354)
Other expense		588	547	1,675	1,699
INCOME (LOSS) FROM CONTINUING OPERATIONS		424	413	754	1,242
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	15	4	15
Reclassification out of Accumulated Other Comprehensive Income | Realized losses on available for sale securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income		0	0
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	15	4	15
Income taxes		0	4	1	4
INCOME (LOSS) FROM CONTINUING OPERATIONS		0	11	3	11
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		99	(9)	221	(53)
Income taxes		24	(3)	53	(13)
INCOME (LOSS) FROM CONTINUING OPERATIONS		75	(6)	168	(40)
Reclassification out of Accumulated Other Comprehensive Income | Amortization of losses
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other expense		(5)	(4)	(13)	(11)
Reclassification out of Accumulated Other Comprehensive Income | Settlement loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other expense		0	0	(8)	0
Reclassification out of Accumulated Other Comprehensive Income | Amortization of unrecognized prior service credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other expense				0	1
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)	(3)	(21)	(10)
Income taxes		(1)	(1)	(5)	(3)
INCOME (LOSS) FROM CONTINUING OPERATIONS		(4)	(2)	(16)	(7)
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		100	(8)	224	(51)
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)	$ (3)	$ (2)

[1] For the three months ended September 30, 2020, we had no net securities gains (losses). For the nine months ended September 30, 2020, net securities gains (losses) totaled $4 million. For the three and nine months ended September 30, 2019, net securities gains (losses) totaled less than $15 million. For the three and nine months ended September 30, 2020, and September 30, 2019, we did not have any impairment losses related to securities.