Securities Available for Sale and Securities Held to Maturity (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013 item		Jun. 30, 2012		Jun. 30, 2013 item		Jun. 30, 2012
Securities Available for Sale and Securities Held to Maturity [Abstract]
Fair Isaac & Company minimum credit score for Prime loan origination	620				620
Net impairment losses on securities	$ 3	[1]	$ 7	[1]	$ 7	[1]	$ 25	[1]

[1] Net impairment losses on securities include total other-than-temporary impairment losses of $2 million and $12 million, net of $(1) million and $5 million reclassified from or recognized in other comprehensive income, for the three months ended June 30, 2013 and 2012, respectively. Net impairment losses on securities include total other-than-temporary impairment losses of $2 million and $14 million, net of $(5) million and $(11) million reclassified from other comprehensive income, for the six months ended June 30, 2013 and 2012, respectively