Loans (Details 6) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Trouble debt restructuring additional information
Trouble debt restructuring average recorded investment	$ 1,178	$ 992	$ 1,164	$ 990
Trouble debt restructuring interest income recognized	11	8	20	15
Commercial loans [Member]
Trouble debt restructuring additional information
Trouble debt restructuring average recorded investment	491	491	492	509
Trouble debt restructuring interest income recognized	4	3	7	6
Consumer loans [Member]
Trouble debt restructuring additional information
Trouble debt restructuring average recorded investment	687	501	672	481
Trouble debt restructuring interest income recognized	7	5	13	9
Construction and other real estate [Member] | Commercial loans [Member]
Trouble debt restructuring additional information
Trouble debt restructuring average recorded investment	360	357	358	373
Trouble debt restructuring interest income recognized	2	2	4	3
Business banking and middle markets enterprises [Member] | Commercial loans [Member]
Trouble debt restructuring additional information
Trouble debt restructuring average recorded investment	96	84	98	87
Trouble debt restructuring interest income recognized
Large corporate [Member] | Commercial loans [Member]
Trouble debt restructuring additional information
Trouble debt restructuring average recorded investment
Trouble debt restructuring interest income recognized
Other commercial [Member] | Commercial loans [Member]
Trouble debt restructuring additional information
Trouble debt restructuring average recorded investment	35	50	36	49
Trouble debt restructuring interest income recognized	2	1	3	3
Residential mortgages [Member] | Consumer loans [Member]
Trouble debt restructuring additional information
Trouble debt restructuring average recorded investment	669	477	653	456
Trouble debt restructuring interest income recognized	7	5	13	8
Credit cards [Member] | Consumer loans [Member]
Trouble debt restructuring additional information
Trouble debt restructuring average recorded investment	18	24	19	25
Trouble debt restructuring interest income recognized				$ 1