Loans and Allowance for Credit Losses, PCI, Accretable Yield (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended	72 Months Ended
	Jun. 30, 2015	Jun. 30, 2015	Dec. 31, 2014
Change in accretable yield related to PCI loans [Abstract]
Total, beginning of period	$ 17,325	$ 17,790	$ 10,447
Addition of accretable yield due to acquisitions	0	0	132
Accretion into interest income	(366)	(764)	(12,783)
Accretion into noninterest income due to sales	0	(28)	(430)
Reclassification from nonaccretable difference for loans with improving credit-related cash flows	8	30	8,568
Changes in expected cash flows that do not affect nonaccretable difference	3	(58)	11,856
Total, end of period	$ 16,970	$ 16,970	$ 17,790