Servicing Activities (Narrative - Mortgage Servicing Advances) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Servicing Activities [Abstract]
Mortgage Servicing Advances Included In Other Assets	$ 78	$ 82
Allowance for uncollected primary servicing advances	$ 1	$ 1

Allowance for uncollected primary servicing advances

No definition available.

Name:	gjm_AllowanceForUncollectedPrimaryServicingAdvances
Namespace Prefix:	gjm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant