Commitments, Contingencies and Guarantees - Commitments (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Commitment Liabilities [Line Items]
Total lending	$ 167,244	$ 137,582
Collateralized agreement	62,093	54,480
Collateralized financing	10,193	15,429
Letters of credit	456	445
Investment	7,879	7,595
Other	6,135	4,892
Total commitments	254,000	220,423
Maturities, Year 1 [Member]
Commitment Liabilities [Line Items]
Total lending	35,364
Collateralized agreement	61,588
Collateralized financing	10,193
Letters of credit	409
Investment	3,623
Other	6,051
Total commitments	117,228
Maturities, Year 2 and Year 3 [Member]
Commitment Liabilities [Line Items]
Total lending	49,229
Collateralized agreement	505
Letters of credit	7
Investment	1,434
Other	84
Total commitments	51,259
Maturities, Year 3 and Year 4 [Member]
Commitment Liabilities [Line Items]
Total lending	71,278
Investment	1,002
Total commitments	72,280
Maturities, Year 5 and Thereafter [Member]
Commitment Liabilities [Line Items]
Total lending	11,373
Letters of credit	40
Investment	1,820
Total commitments	13,233
Investment Grade Commercial Lending [Member]
Commitment Liabilities [Line Items]
Total lending	89,276	81,729
Investment Grade Commercial Lending [Member] | Maturities, Year 1 [Member]
Commitment Liabilities [Line Items]
Total lending	13,921
Investment Grade Commercial Lending [Member] | Maturities, Year 2 and Year 3 [Member]
Commitment Liabilities [Line Items]
Total lending	31,099
Investment Grade Commercial Lending [Member] | Maturities, Year 3 and Year 4 [Member]
Commitment Liabilities [Line Items]
Total lending	43,303
Investment Grade Commercial Lending [Member] | Maturities, Year 5 and Thereafter [Member]
Commitment Liabilities [Line Items]
Total lending	953
Non Investment Grade Commercial Lending [Member]
Commitment Liabilities [Line Items]
Total lending	58,718	51,793
Non Investment Grade Commercial Lending [Member] | Maturities, Year 1 [Member]
Commitment Liabilities [Line Items]
Total lending	6,130
Non Investment Grade Commercial Lending [Member] | Maturities, Year 2 and Year 3 [Member]
Commitment Liabilities [Line Items]
Total lending	15,810
Non Investment Grade Commercial Lending [Member] | Maturities, Year 3 and Year 4 [Member]
Commitment Liabilities [Line Items]
Total lending	26,379
Non Investment Grade Commercial Lending [Member] | Maturities, Year 5 and Thereafter [Member]
Commitment Liabilities [Line Items]
Total lending	10,399
Warehouse Financing [Member]
Commitment Liabilities [Line Items]
Total lending	5,581	$ 4,060
Warehouse Financing [Member] | Maturities, Year 1 [Member]
Commitment Liabilities [Line Items]
Total lending	1,644
Warehouse Financing [Member] | Maturities, Year 2 and Year 3 [Member]
Commitment Liabilities [Line Items]
Total lending	2,320
Warehouse Financing [Member] | Maturities, Year 3 and Year 4 [Member]
Commitment Liabilities [Line Items]
Total lending	1,596
Warehouse Financing [Member] | Maturities, Year 5 and Thereafter [Member]
Commitment Liabilities [Line Items]
Total lending	21
Credit card [Member]
Commitment Liabilities [Line Items]
Total lending	13,669
Credit card [Member] | Maturities, Year 1 [Member]
Commitment Liabilities [Line Items]
Total lending	$ 13,669