Loans - Wholesale RealEstate Loans, Credit Rating (Details 2) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Wholesale Real Estate Loans
Retained loans	$ 712,898	$ 718,997	$ 675,437
Wholesale
Wholesale Real Estate Loans
Retained loans	283,653	278,395
Wholesale | Commercial and industrial [Member]
Wholesale Real Estate Loans
Retained loans	97,089	94,215
Wholesale | Real estate [Member]
Wholesale Real Estate Loans
Retained loans	56,747	54,684
Criticized exposure	4,408	4,792
% of criticized exposure to total real estate retained loans	7.77%	8.76%
Criticized nonaccrual	809	886
% of criticized nonaccrual to total real estate retained loans	1.43%	1.62%
Wholesale | Multi-family [Member]
Wholesale Real Estate Loans
Retained loans	33,516	32,524
Criticized exposure	2,221	2,451
% of criticized exposure to total real estate retained loans	6.63%	7.54%
Criticized nonaccrual	396	412
% of criticized nonaccrual to total real estate retained loans	1.18%	1.27%
Wholesale | Commercial lessors [Member]
Wholesale Real Estate Loans
Retained loans	15,311	14,444
Criticized exposure	1,750	1,662
% of criticized exposure to total real estate retained loans	11.43%	11.51%
Criticized nonaccrual	302	284
% of criticized nonaccrual to total real estate retained loans	1.97%	1.97%
Wholesale | Commercial construction and development [Member]
Wholesale Real Estate Loans
Retained loans	3,187	3,148
Criticized exposure	260	297
% of criticized exposure to total real estate retained loans	8.16%	9.43%
Criticized nonaccrual	34	69
% of criticized nonaccrual to total real estate retained loans	1.07%	2.19%
Wholesale | Wholesale Realestate Others [Member]
Wholesale Real Estate Loans
Retained loans	4,733	4,568
Criticized exposure	177	382
% of criticized exposure to total real estate retained loans	3.74%	8.36%
Criticized nonaccrual	77	121
% of criticized nonaccrual to total real estate retained loans	1.63%	2.65%
Wholesale | Financial institutions [Member]
Wholesale Real Estate Loans
Retained loans	35,629	38,219
Wholesale | Government agencies [Member]
Wholesale Real Estate Loans
Retained loans	7,814	7,819
Wholesale | Other [Member]
Wholesale Real Estate Loans
Retained loans	$ 86,374	$ 83,458