Fair Values of Assets and Liabilities - Fair Value Option (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Fair value carrying amount, total loans	$ 2,550	$ 2,011
Contractual principal outstanding, total loans	2,528	1,994
Carrying amount over (under) contractual principal outstanding, total loans	22	17
Fair value carrying amount, time deposits	6,089	2,818
Contractual principal outstanding, time deposits	6,104	2,822
Carrying amount over (under) contractual principal outstanding, time deposits	(15)	(4)
Fair value, nonaccrual loans	1	1
Contractual principal outstanding, nonaccrual loans	1	1
Fair value, loans 90 days or more past due	2	4
Contractual principal outstanding, loans 90 days or more past due	$ 2	$ 4

Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2E
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2E

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

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This item represents the difference between the aggregate fair value and the aggregate unpaid principal balance of loans and long-term receivables (other than securities categorized as trading, available-for-sale or held-to-maturity) that have contractual principal amounts and for which the fair value option has been elected.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
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-Subparagraph (d)(1)
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This item represents the aggregate fair value of loans held as assets that are 90 days or more past due for which the fair value option has been elected.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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This item represents the aggregate fair value of loans held as assets that are in nonaccrual status for which the fair value option has been elected, if the entity's policy is to recognize interest income separately from other changes in fair value.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
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-SubTopic 10
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- Definition

Fair value portion of mortgage loans held-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

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Fair Value Option Loans Held As Assets Aggregate Amount In Nonaccrual Status Aggregate Unpaid Principal

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Fair Value Option Loans Held As Assets Contractual Principal

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Fair Value Option Loans Held As Assets Ninety Days Or More Past Due Aggregate Unpaid Principal

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Fair value option time deposits carrying amount over under contractual principal outstanding.

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Fair value option time deposits contractual principal outstanding.

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