Commitments, Contingencies and Guarantees - Commitments (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Commitment Liabilities [Line Items]
Total commitments to extend credit	$ 116,092	$ 117,158
Contingent and forward starting resale and securities borrowing agreements	40,563	28,874
Forward starting repurchase and secured lending agreements	12,762	5,878
Letters of credit	341	249
Investment commitments	5,705	6,054
Other	5,461	6,944
Total commitments	180,924	165,157
Maturities, Remainder of Current Fiscal Year [Member]
Commitment Liabilities [Line Items]
Total commitments to extend credit	4,065
Contingent and forward starting resale and securities borrowing agreements	40,505
Forward starting repurchase and secured lending agreements	12,762
Letters of credit	11
Investment commitments	2,307
Other	5,020
Total commitments	64,670
Maturities, Year 2 and Year 3 [Member]
Commitment Liabilities [Line Items]
Total commitments to extend credit	22,551
Contingent and forward starting resale and securities borrowing agreements	58
Letters of credit	323
Investment commitments	2,232
Other	331
Total commitments	25,495
Maturities, Year 3 and Year 4 [Member]
Commitment Liabilities [Line Items]
Total commitments to extend credit	51,845
Letters of credit	3
Investment commitments	42
Other	60
Total commitments	51,950
Maturities, Year 5 and Thereafter [Member]
Commitment Liabilities [Line Items]
Total commitments to extend credit	37,631
Letters of credit	4
Investment commitments	1,124
Other	50
Total commitments	38,809
Investment Grade Commercial Lending [Member]
Commitment Liabilities [Line Items]
Total commitments to extend credit	75,995	72,428
Investment Grade Commercial Lending [Member] | Maturities, Remainder of Current Fiscal Year [Member]
Commitment Liabilities [Line Items]
Total commitments to extend credit	3,560
Investment Grade Commercial Lending [Member] | Maturities, Year 2 and Year 3 [Member]
Commitment Liabilities [Line Items]
Total commitments to extend credit	13,576
Investment Grade Commercial Lending [Member] | Maturities, Year 3 and Year 4 [Member]
Commitment Liabilities [Line Items]
Total commitments to extend credit	36,502
Investment Grade Commercial Lending [Member] | Maturities, Year 5 and Thereafter [Member]
Commitment Liabilities [Line Items]
Total commitments to extend credit	22,357
Non Investment Grade Commercial Lending [Member]
Commitment Liabilities [Line Items]
Total commitments to extend credit	35,938	41,277
Non Investment Grade Commercial Lending [Member] | Maturities, Remainder of Current Fiscal Year [Member]
Commitment Liabilities [Line Items]
Total commitments to extend credit	505
Non Investment Grade Commercial Lending [Member] | Maturities, Year 2 and Year 3 [Member]
Commitment Liabilities [Line Items]
Total commitments to extend credit	6,989
Non Investment Grade Commercial Lending [Member] | Maturities, Year 3 and Year 4 [Member]
Commitment Liabilities [Line Items]
Total commitments to extend credit	14,772
Non Investment Grade Commercial Lending [Member] | Maturities, Year 5 and Thereafter [Member]
Commitment Liabilities [Line Items]
Total commitments to extend credit	13,672
Warehouse Financing [Member]
Commitment Liabilities [Line Items]
Total commitments to extend credit	4,159	$ 3,453
Warehouse Financing [Member] | Maturities, Year 2 and Year 3 [Member]
Commitment Liabilities [Line Items]
Total commitments to extend credit	1,986
Warehouse Financing [Member] | Maturities, Year 3 and Year 4 [Member]
Commitment Liabilities [Line Items]
Total commitments to extend credit	571
Warehouse Financing [Member] | Maturities, Year 5 and Thereafter [Member]
Commitment Liabilities [Line Items]
Total commitments to extend credit	$ 1,602