Contingencies and Other Risks - Narrative (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Mar. 31, 2014
Contingencies and Other Risks [Abstract]
CFPB Settlement	$ 98
Representation And Warranty Obligations Reserve Balance	$ 45	$ 46

Representation And Warranty Obligations Reserve Balance

No definition available.

Name:	ally_RepresentationAndWarrantyObligationsReserveBalance
Namespace Prefix:	ally_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant