Securities (Schedule of Credit Losses on Securities with OTTI, Excluding Securities Acquired from the FDIC, Where a Portion of the Unrealized Loss was Recognized in OCI (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Securities
Balance at beginning of period	$ 78	$ 98	$ 130
Credit losses on securities without previous OTTI	6	0	0
Credit losses on securities for which OTTI was previously recognized	0	0	5
Reductions for securities sold/settled during the period	(17)	(20)	(37)
Credit recoveries through yield	(3)	0	0
Balance at end of period	$ 64	$ 78	$ 98