Loans and Allowance for Credit Losses, PCI, Accretable Yield (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended	48 Months Ended
Sep. 30, 2013	Sep. 30, 2013	Dec. 31, 2012
Change in accretable yield related to PCI loans [Abstract]
Total, beginning of period	$ 20,021	$ 18,548	$ 10,447
Addition of accretable yield due to acquisitions	1	1	131
Accretion into interest income	(481)	(1,386)	(9,351)
Accretion into noninterest income due to sales	0	(151)	(242)
Reclassification from nonaccretable difference for loans with improving credit-related cash flows	9	916	5,354
Changes in expected cash flows that do not affect nonaccretable difference	(34)	1,588	12,209
Total, end of period	$ 19,516	$ 19,516	$ 18,548

The aggregate excess of a loan's cash flows expected to be collected over the investor's initial investment in the loan. This relates to loans not accounted for as debt securities, with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

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The change in the estimate of cash flows expected to be collected, after acquisition of loans, which results in an increase in accretable yield (for example, if actual cash flows are significantly greater than previously expected). This relates to loans not accounted for as debt securities, with evidence of deterioration of credit quality since origination that was acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

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