Loans and ACL (Nonperforming Assets and Past Due Loans) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
NPLs held for investment	$ 1,149	$ 1,380
Foreclosed real estate	89	107
Other foreclosed property	38	49
Total NPAs (excluding covered assets)	1,276	1,536
Loans 90 days or more past due and still accruing (excluding covered loans)	123	167
Foreclosed real estate covered by FDIC loss sharing agreements	181	254
Mortgage loans guaranteed by GNMA that are 90 days or more past due not required to be repurchased	492	517
Loans past due 90 days or more covered by FDIC loss sharing agreements	401	442
Mortgage loans 90 days or more past due government guaranteed	$ 244	$ 252