Accumulated Other Comprehensive Income (Loss) (Narrative) (Details) (Non-Agency Residential Mortgage-Backed Securities [Member], USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Non-Agency Residential Mortgage-Backed Securities [Member]
Unrealized loss on other-than-temporarily impaired securities (excluding covered), pre-tax	$ 11	$ 55