Segment information (Details 1) (USD $) In Millions	3 Months Ended		12 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Summary of segment information
Average total assets	$ 70,262	$ 68,607	$ 68,380
Business Banking [Member]
Summary of segment information
Average total assets	4,861	4,884	4,843
Commercial Banking [Member]
Summary of segment information
Average total assets	16,856	15,504	15,461
Commercial Real Estate [Member]
Summary of segment information
Average total assets	14,227	13,255	13,194
Discretionary Portfolio [Member]
Summary of segment information
Average total assets	14,012	14,699	14,690
Residential Mortgage Banking [Member]
Summary of segment information
Average total assets	1,940	2,188	2,217
Retail Banking [Member]
Summary of segment information
Average total assets	11,776	12,191	12,079
All Other [Member]
Summary of segment information
Average total assets	$ 6,590	$ 5,886	$ 5,896