Investment In Operating Leases, Net (Schedule Of Depreciation Expense On Operating Lease Assets) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Leases, Operating [Abstract]
Depreciation Expense On Operating Lease Assets	$ 691	$ 651
Gross Remarketing (Gains) Losses	(69)ally_GrossRemarketingGainsLosses	(109)ally_GrossRemarketingGainsLosses
Depreciation expense on operating lease assets	$ 622	$ 542

The total depreciation charge recorded for property subject to or held for lease.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Name:	us-gaap_OperatingLeasesIncomeStatementDepreciationExpenseOnPropertySubjectToOrHeldForLease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration