Loans - Wholesale Loan Portfolio - By Class of Receivable (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 844,195	$ 832,792	$ 756,971
Wholesale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 364,312	$ 357,050	$ 331,219
% of total criticized exposure to total retained loans	2.80%	2.06%
% of criticized nonaccrual to total retained loans	0.60%	0.28%
Wholesale | Current and less than 30 days past due and still accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 360,405	$ 354,451
Wholesale | 30–89 days past due and still accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	1,490	1,544
Wholesale | 90 or more days past due and still accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	214	67
Wholesale | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	2,203	988
Wholesale | Total non-U.S.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	95,874	94,051
Wholesale | Total U.S.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	268,438	262,999
Wholesale | Investment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	269,693	267,736
Wholesale | Total noninvestment- grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	94,619	89,314
Wholesale | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	84,406	81,953
Wholesale | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	8,010	6,373
Wholesale | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	2,203	988
Wholesale | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 119,306	$ 112,932
% of total criticized exposure to total retained loans	6.83%	4.56%
% of criticized nonaccrual to total retained loans	1.44%	0.54%
Wholesale | Commercial and industrial | Current and less than 30 days past due and still accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 117,203	$ 112,058
Wholesale | Commercial and industrial | 30–89 days past due and still accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	360	259
Wholesale | Commercial and industrial | 90 or more days past due and still accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	21	7
Wholesale | Commercial and industrial | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	1,722	608
Wholesale | Commercial and industrial | Total non-U.S.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	32,037	30,063
Wholesale | Commercial and industrial | Total U.S.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	87,269	82,869
Wholesale | Commercial and industrial | Investment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	63,651	62,150
Wholesale | Commercial and industrial | Total noninvestment- grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	55,655	50,782
Wholesale | Commercial and industrial | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	47,501	45,632
Wholesale | Commercial and industrial | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	6,432	4,542
Wholesale | Commercial and industrial | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	1,722	608
Wholesale | Real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 96,101	$ 92,820
% of total criticized exposure to total retained loans	1.44%	1.60%
% of criticized nonaccrual to total retained loans	0.26%	0.25%
Wholesale | Real estate | Current and less than 30 days past due and still accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 95,680	$ 92,381
Wholesale | Real estate | 30–89 days past due and still accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	161	193
Wholesale | Real estate | 90 or more days past due and still accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	7	15
Wholesale | Real estate | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	253	231
Wholesale | Real estate | Total non-U.S.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	3,231	3,003
Wholesale | Real estate | Total U.S.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	92,870	89,817
Wholesale | Real estate | Investment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	77,064	74,330
Wholesale | Real estate | Total noninvestment- grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	19,037	18,490
Wholesale | Real estate | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	17,652	17,008
Wholesale | Real estate | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	1,132	1,251
Wholesale | Real estate | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	253	231
Wholesale | Financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 28,828	$ 29,783
% of total criticized exposure to total retained loans	1.13%	1.11%
% of criticized nonaccrual to total retained loans	0.04%	0.03%
Wholesale | Financial institutions | Current and less than 30 days past due and still accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 28,761	$ 29,713
Wholesale | Financial institutions | 30–89 days past due and still accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	32	49
Wholesale | Financial institutions | 90 or more days past due and still accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	24	11
Wholesale | Financial institutions | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	11	10
Wholesale | Financial institutions | Total non-U.S.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	16,405	17,166
Wholesale | Financial institutions | Total U.S.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	12,423	12,617
Wholesale | Financial institutions | Investment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	21,558	21,786
Wholesale | Financial institutions | Total noninvestment- grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	7,270	7,997
Wholesale | Financial institutions | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	6,943	7,667
Wholesale | Financial institutions | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	316	320
Wholesale | Financial institutions | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	11	10
Wholesale | Government agencies
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 11,912	$ 11,626
% of total criticized exposure to total retained loans	0.05%	0.06%
% of criticized nonaccrual to total retained loans	0.00%	0.00%
Wholesale | Government agencies | Current and less than 30 days past due and still accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 11,909	$ 11,565
Wholesale | Government agencies | 30–89 days past due and still accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	1	55
Wholesale | Government agencies | 90 or more days past due and still accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	2	6
Wholesale | Government agencies | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	0	0
Wholesale | Government agencies | Total non-U.S.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	1,929	1,788
Wholesale | Government agencies | Total U.S.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	9,983	9,838
Wholesale | Government agencies | Investment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	11,457	11,363
Wholesale | Government agencies | Total noninvestment- grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	455	263
Wholesale | Government agencies | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	449	256
Wholesale | Government agencies | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	6	7
Wholesale | Government agencies | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	0	0
Wholesale | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 108,165	$ 109,889
% of total criticized exposure to total retained loans	0.32%	0.36%
% of criticized nonaccrual to total retained loans	0.20%	0.13%
Wholesale | Other | Current and less than 30 days past due and still accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 106,852	$ 108,734
Wholesale | Other | 30–89 days past due and still accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	936	988
Wholesale | Other | 90 or more days past due and still accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	160	28
Wholesale | Other | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	217	139
Wholesale | Other | Total non-U.S.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	42,272	42,031
Wholesale | Other | Total U.S.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	65,893	67,858
Wholesale | Other | Investment-grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	95,963	98,107
Wholesale | Other | Total noninvestment- grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	12,202	11,782
Wholesale | Other | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	11,861	11,390
Wholesale | Other | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	124	253
Wholesale | Other | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 217	$ 139