Segment information (Details 1) (USD $) In Millions, unless otherwise specified	6 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Summary of segment information
Segment Reporting Information Average Asset	$ 79,056	$ 70,262	$ 73,977
Business Banking [Member]
Summary of segment information
Segment Reporting Information Average Asset	4,932	4,861	5,192
Commercial Banking [Member]
Summary of segment information
Segment Reporting Information Average Asset	19,455	16,856	17,650
Commercial Real Estate [Member]
Summary of segment information
Segment Reporting Information Average Asset	16,316	14,227	15,025
Discretionary Portfolio [Member]
Summary of segment information
Segment Reporting Information Average Asset	16,136	14,012	14,170
Residential Mortgage Banking [Member]
Summary of segment information
Segment Reporting Information Average Asset	2,200	1,940	1,958
Retail Banking [Member]
Summary of segment information
Segment Reporting Information Average Asset	11,791	11,776	11,940
All Other [Member]
Summary of segment information
Segment Reporting Information Average Asset	$ 8,226	$ 6,590	$ 8,042