Loans (Details 11) (Commercial Loan [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Average balance of impaired commercial loans:
Total average balance of impaired commercial loans	$ 905	$ 1,097	$ 996	$ 1,106
Interest income recognized on impaired commercial loans:
Total interest income recognized on impaired commercial loans	3	3	6	6
Construction and other real estate [Member]
Average balance of impaired commercial loans:
Total average balance of impaired commercial loans	624	759	660	757
Interest income recognized on impaired commercial loans:
Total interest income recognized on impaired commercial loans	1	2	3	3
Business banking and middle markets enterprises [Member]
Average balance of impaired commercial loans:
Total average balance of impaired commercial loans	127	161	127	158
Interest income recognized on impaired commercial loans:
Total interest income recognized on impaired commercial loans	1	1	2	2
Large corporate [Member]
Average balance of impaired commercial loans:
Total average balance of impaired commercial loans	66	74	90	84
Interest income recognized on impaired commercial loans:
Total interest income recognized on impaired commercial loans
Other commercial [Member]
Average balance of impaired commercial loans:
Total average balance of impaired commercial loans	88	103	89	107
Interest income recognized on impaired commercial loans:
Total interest income recognized on impaired commercial loans	$ 1		$ 1	$ 1