Investment In Operating Leases, Net (Schedule Of Depreciation Expense On Operating Lease Assets) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Leases, Operating [Abstract]
Depreciation Expense On Operating Lease Assets	$ 2,666	$ 2,327	$ 1,515
Gross Remarketing (Gains) Losses	(433)ally_GrossRemarketingGainsLosses	(332)ally_GrossRemarketingGainsLosses	(116)ally_GrossRemarketingGainsLosses
Depreciation expense on operating lease assets	$ 2,233	$ 1,995	$ 1,399

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