Leasing (Depreciation Expense on Operating Lease Assets) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2024	Mar. 31, 2023
Leases [Abstract]
Operating lease revenue	$ 356	$ 402
Depreciation expense on operating lease assets (excluding remarketing gains)	250	273
Remarketing gains, net	(46)	(47)
Net depreciation expense on operating lease assets	204	226
Variable lease payments, excessive wear and tear	$ 4	$ 2

Depreciation expense on operating lease assets (excluding remarketing gains).

No definition available.

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- Definition

Remarketing gains (losses), net

+ References

No definition available.

+ Details

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- Definition

Variable lease payments related to excess mileage and wear and tear on operating lease vehicles.

+ References

No definition available.

+ Details

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Namespace Prefix:	ally_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- References

No definition available.

+ Details

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- Definition

Amount of operating lease income from lease payments and variable lease payments paid and payable to lessor. Includes, but is not limited to, variable lease payments not included in measurement of lease receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479773/842-30-50-5

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 270
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482964/270-10-50-6A

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479016/842-30-45-3

+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

Amount of depreciation expense for lessor's underlying asset for which right to use has been conveyed to lessee under operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479773/842-30-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 360
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482099/360-10-50-1

+ Details

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