Derivative Instruments And Hedging Activities (Narrative) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Cash and securities collateral placed with counterparties	$ 220	$ 328
Non-derivative collateral placed with counterparties	18	18
Cash collateral received from counterparties	60	159
noncash collateral received	$ 17	$ 18

The amount of the right to reclaim collateral under legally enforceable agreements that enable the posting and receiving of collateral associated with the fair value of our derivative positions on an ongoing basis.

No definition available.

Name:	ally_CashAndSecuritiesCollateralPlacedWithCounterparties
Namespace Prefix:	ally_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant