Commitments and Contingencies - Pledged Assets (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Loans and leases (including $14 and $15 at fair value, respectively)	$ 307,224	$ 312,061
Asset Pledged as Collateral
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Securities, fair value	40,105	41,270
Federal Reserve Bank Advances [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	53,548	55,252
Federal Reserve Bank Advances [Member] \| Asset Pledged as Collateral
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Loans and leases (including $14 and $15 at fair value, respectively)	71,692	73,898
FHLB Advances
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	25,031	24,712
FHLB Advances \| Asset Pledged as Collateral
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Loans and leases (including $14 and $15 at fair value, respectively)	$ 66,946	$ 67,748

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.

No definition available.

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Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

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- Definition

Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481990/310-10-45-2

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-4

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- Definition

Amount of investment in marketable security.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(2))
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-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

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-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.4)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479853/942-210-S99-1

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