Accumulated Other Comprehensive (Loss) Income - Schedule of Pretax and After-tax Components of Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI activity before reclassification, net amount			$ (165)	$ (747)
Net realized losses on sales of investment securities available for sale	$ 12	$ 0	26	0
Benefit for investment securities available for sale credit losses	(3)	0	0	0
Amounts reclassified from AOCI to earnings, Net Amount			20	8
Other comprehensive loss on securities available for sale, gross amount	(146)	(346)	(197)	(973)
Other comprehensive loss on securities available for sale, gross amount, tax	38	82	52	234
Other comprehensive loss, net of tax	(108)	(264)	(145)	(739)
Unrealized loss on securities available for sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI activity before reclassification, gross amount	(155)	(348)	(229)	(983)
AOCI activity before reclassification, tax	40	82	60	236
AOCI activity before reclassification, net amount	(115)	(266)	(169)	(747)
Other comprehensive loss on securities available for sale, gross amount	(146)	(348)	(203)	(983)
Other comprehensive loss on securities available for sale, gross amount, tax	38	82	53	236
Other comprehensive loss, net of tax	(108)	(266)	(150)	(747)
Unrealized loss on securities available for sale \| $12 realized loss on sales of investment securities available for sale, net; $(3) provision for credit losses
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI to earnings, gross amount	9	0	26	0
Amounts reclassified from AOCI to earnings, tax	(2)	0	(7)	0
Amounts reclassified from AOCI to earnings, Net Amount	7	0	19	0
Unrealized loss on securities available for sale transferred to held to maturity
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI activity before reclassification, gross amount	0	0	0	0
AOCI activity before reclassification, tax	0	0	0	0
AOCI activity before reclassification, net amount	0	0	0	0
Amounts reclassified from AOCI to earnings, Net Amount			1	1
Other comprehensive loss on securities available for sale, gross amount	0	0	1	1
Other comprehensive loss on securities available for sale, gross amount, tax	0	0	0	0
Other comprehensive loss, net of tax	0	0	1	1
Unrealized loss on securities available for sale transferred to held to maturity \| Interest on investment securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI to earnings, gross amount	0	0	1	1
Amounts reclassified from AOCI to earnings, tax	0	0	0	0
Amounts reclassified from AOCI to earnings, Net Amount	0	0	1	1
Defined benefit pension items
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI activity before reclassification, gross amount	0	0	5	0
AOCI activity before reclassification, tax	0	0	(1)	0
AOCI activity before reclassification, net amount	0	0	4	0
Amounts reclassified from AOCI to earnings, Net Amount			0	7
Other comprehensive loss on securities available for sale, gross amount	0	2	5	9
Other comprehensive loss on securities available for sale, gross amount, tax	0	0	(1)	(2)
Other comprehensive loss, net of tax	0	2	4	7
Defined benefit pension items \| Other noninterest expense
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI to earnings, gross amount	0	2	0	9
Amounts reclassified from AOCI to earnings, tax	0	0	0	(2)
Amounts reclassified from AOCI to earnings, Net Amount	$ 0	$ 2	$ 0	$ 7

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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