Loans and ACL (Nonperforming Assets and Past Due Loans) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
NPLs held for investment	$ 1,030	$ 1,380
Foreclosed real estate	85	107
Other foreclosed property	47	49
Total NPAs (excluding covered assets)	1,162	1,536
Loans 90 days or more past due and still accruing (excluding covered loans)	122	167
Foreclosed real estate covered by FDIC loss sharing agreements	148	254
Mortgage loans guaranteed by GNMA that are 90 days or more past due not required to be repurchased	497	517
Loans past due 90 days or more covered by FDIC loss sharing agreements	364	442
Mortgage loans 90 days or more past due government guaranteed	$ 266	$ 252