Securities (Details 7) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Securities held to maturity
Over One Year Through Five Years, Carrying Amount	$ 295
Over Five Years Through Ten Years, Carrying Amount	1,304
Over Ten Years, Carrying Amount	6,578
Total securities held to maturity, carrying amount	8,177	6,509
Over One Year Through Five Years, Fair Value	297
Over Five Years Through Ten Years, Fair Value	1,344
Over Ten Years, Fair Value	6,610
Total securities held to maturity, Fair Value	8,251	6,439
Residential mortgage-backed securities, U.S. government agency and government-sponsored agencies
Securities held to maturity
Over One Year Through Five Years, Carrying Amount	2
Over Ten Years, Carrying Amount	5,667
Total securities held to maturity, carrying amount	5,669	4,995
Over One Year Through Five Years, Fair Value	2
Over Ten Years, Fair Value	5,696
Total securities held to maturity, Fair Value	5,698	4,934
U.S. Treasury
Securities held to maturity
Over One Year Through Five Years, Carrying Amount	244
Over Five Years Through Ten Years, Carrying Amount	240
Total securities held to maturity, carrying amount	484
Over One Year Through Five Years, Fair Value	245
Over Five Years Through Ten Years, Fair Value	241
Total securities held to maturity, Fair Value	486
U.S. government sponsored agencies
Securities held to maturity
Over Five Years Through Ten Years, Carrying Amount	275
Total securities held to maturity, carrying amount	275
Over Five Years Through Ten Years, Fair Value	275
Total securities held to maturity, Fair Value	275
U.S. government agency and government-sponsored agencies - commercial mortgage-backed securities
Securities held to maturity
Over One Year Through Five Years, Carrying Amount	49
Over Five Years Through Ten Years, Carrying Amount	789
Over Ten Years, Carrying Amount	911
Total securities held to maturity, carrying amount	1,749	1,514
Over One Year Through Five Years, Fair Value	50
Over Five Years Through Ten Years, Fair Value	828
Over Ten Years, Fair Value	914
Total securities held to maturity, Fair Value	$ 1,792	$ 1,505