Loans - Wholesale Loan Portfolio - Real Estate Class of Loans (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	$ 747,508	$ 724,177	$ 726,835
Wholesale
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	324,502	308,263	306,222
% of total criticized to total retained loans	1.45%	2.02%
% of nonaccrual loans to total retained loans	0.18%	0.27%
Wholesale | Real Estate Multifamily
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	51,049	44,389
% of total criticized to total retained loans	1.28%	2.57%
% of nonaccrual loans to total retained loans	0.25%	0.43%
Wholesale | Real Estate Commercial lessors
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	17,438	15,949
% of total criticized to total retained loans	4.82%	8.30%
% of nonaccrual loans to total retained loans	0.63%	0.90%
Wholesale | Real Estate Commercial construction and development
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	4,264	3,674
% of total criticized to total retained loans	0.98%	2.20%
% of nonaccrual loans to total retained loans	0.00%	0.08%
Wholesale | Real Estate Other
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	6,362	5,139
% of total criticized to total retained loans	0.49%	0.56%
% of nonaccrual loans to total retained loans	0.27%	0.18%
Wholesale | Real estate
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	79,113	69,151
% of total criticized to total retained loans	1.98%	3.72%
% of nonaccrual loans to total retained loans	0.32%	0.50%
Wholesale | Criticized | Real Estate Multifamily
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	652	1,142
Wholesale | Criticized | Real Estate Commercial lessors
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	841	1,323
Wholesale | Criticized | Real Estate Commercial construction and development
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	42	81
Wholesale | Criticized | Real Estate Other
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	31	29
Wholesale | Criticized | Real estate
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	1,566	2,575
Wholesale | Criticized nonaccrual
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	599	821
Wholesale | Criticized nonaccrual | Real Estate Multifamily
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	126	191
Wholesale | Criticized nonaccrual | Real Estate Commercial lessors
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	110	143
Wholesale | Criticized nonaccrual | Real Estate Commercial construction and development
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	0	3
Wholesale | Criticized nonaccrual | Real Estate Other
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	17	9
Wholesale | Criticized nonaccrual | Real estate
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	$ 253	$ 346