Derivative Instruments And Hedging Activities (Narrative) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Cash and securities collateral placed with counterparties	$ 447	$ 1,290
Cash collateral received from counterparties	565	941
noncash collateral received	$ 1	$ 0

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:	gjm_CashAndSecuritiesCollateralPlacedWithCounterparties
Namespace Prefix:	gjm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant