Variable Interest Entities - Nonconsolidated Variable Interest Entities (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Assets in VIE	$ 145,175		$ 128,069
Carrying Value of the Firm's Variable Interests in Nonconsolidated VIEs - Assets	1,132,059	$ 1,141,523	992,968
Carrying Value of the Firm's Variable Interests in Nonconsolidated VIEs - Liabilities	1,039,409	$ 1,051,494	902,703
Maximum Exposure to Loss in Nonconsolidated VIEs	20,815		20,786
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Carrying Value of the Firm's Variable Interests in Nonconsolidated VIEs - Assets	9,746		9,526
Carrying Value of the Firm's Variable Interests in Nonconsolidated VIEs - Liabilities	978		619
Retained Interests, Maximum Exposure to Loss [Member]
Variable Interest Entity [Line Items]
Maximum Exposure to Loss in Nonconsolidated VIEs	3,848		3,372
Purchased Interests, Maximum Exposure to Loss [Member]
Variable Interest Entity [Line Items]
Maximum Exposure to Loss in Nonconsolidated VIEs	1,630		901
Commitments and Guarantees, Maximum Exposure to Loss [Member]
Variable Interest Entity [Line Items]
Maximum Exposure to Loss in Nonconsolidated VIEs	2,806		2,697
Derivatives, Maximum Exposure to Loss [Member]
Variable Interest Entity [Line Items]
Maximum Exposure to Loss in Nonconsolidated VIEs	8,653		9,010
Debt and equity, Maximum Exposure to Loss [Member]
Variable Interest Entity [Line Items]
Maximum Exposure to Loss in Nonconsolidated VIEs	3,878		4,806
Mortgage-Backed [Member]
Variable Interest Entity [Line Items]
Assets in VIE	93,867		75,354
Maximum Exposure to Loss in Nonconsolidated VIEs	4,888		3,946
Mortgage-Backed [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Carrying Value of the Firm's Variable Interests in Nonconsolidated VIEs - Assets	4,467		3,830
Mortgage-Backed [Member] | Retained Interests, Maximum Exposure to Loss [Member]
Variable Interest Entity [Line Items]
Maximum Exposure to Loss in Nonconsolidated VIEs	3,689		3,223
Mortgage-Backed [Member] | Purchased Interests, Maximum Exposure to Loss [Member]
Variable Interest Entity [Line Items]
Maximum Exposure to Loss in Nonconsolidated VIEs	778		607
Mortgage-Backed [Member] | Commitments and Guarantees, Maximum Exposure to Loss [Member]
Variable Interest Entity [Line Items]
Maximum Exposure to Loss in Nonconsolidated VIEs	45		50
Mortgage-Backed [Member] | Derivatives, Maximum Exposure to Loss [Member]
Variable Interest Entity [Line Items]
Maximum Exposure to Loss in Nonconsolidated VIEs	376		66
Corporate debt and other asset-backed [Member]
Variable Interest Entity [Line Items]
Assets in VIE	14,990		16,248
Maximum Exposure to Loss in Nonconsolidated VIEs	10,843		11,821
Corporate debt and other asset-backed [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Carrying Value of the Firm's Variable Interests in Nonconsolidated VIEs - Assets	1,666		2,040
Carrying Value of the Firm's Variable Interests in Nonconsolidated VIEs - Liabilities	968		612
Corporate debt and other asset-backed [Member] | Retained Interests, Maximum Exposure to Loss [Member]
Variable Interest Entity [Line Items]
Maximum Exposure to Loss in Nonconsolidated VIEs	159		149
Corporate debt and other asset-backed [Member] | Purchased Interests, Maximum Exposure to Loss [Member]
Variable Interest Entity [Line Items]
Maximum Exposure to Loss in Nonconsolidated VIEs	852		294
Corporate debt and other asset-backed [Member] | Commitments and Guarantees, Maximum Exposure to Loss [Member]
Variable Interest Entity [Line Items]
Maximum Exposure to Loss in Nonconsolidated VIEs	1,378		1,374
Corporate debt and other asset-backed [Member] | Derivatives, Maximum Exposure to Loss [Member]
Variable Interest Entity [Line Items]
Maximum Exposure to Loss in Nonconsolidated VIEs	8,189		8,849
Corporate debt and other asset-backed [Member] | Debt and equity, Maximum Exposure to Loss [Member]
Variable Interest Entity [Line Items]
Maximum Exposure to Loss in Nonconsolidated VIEs	265		1,155
Real estate, credit- and power-related and other investing [Member]
Variable Interest Entity [Line Items]
Assets in VIE	20,696		19,602
Maximum Exposure to Loss in Nonconsolidated VIEs	4,593		4,543
Real estate, credit- and power-related and other investing [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Carrying Value of the Firm's Variable Interests in Nonconsolidated VIEs - Assets	3,204		3,243
Carrying Value of the Firm's Variable Interests in Nonconsolidated VIEs - Liabilities	10		7
Real estate, credit- and power-related and other investing [Member] | Commitments and Guarantees, Maximum Exposure to Loss [Member]
Variable Interest Entity [Line Items]
Maximum Exposure to Loss in Nonconsolidated VIEs	1,304		1,213
Real estate, credit- and power-related and other investing [Member] | Derivatives, Maximum Exposure to Loss [Member]
Variable Interest Entity [Line Items]
Maximum Exposure to Loss in Nonconsolidated VIEs	85		92
Real estate, credit- and power-related and other investing [Member] | Debt and equity, Maximum Exposure to Loss [Member]
Variable Interest Entity [Line Items]
Maximum Exposure to Loss in Nonconsolidated VIEs	3,204		3,238
Investment In Funds [Member]
Variable Interest Entity [Line Items]
Assets in VIE	15,622		16,865
Maximum Exposure to Loss in Nonconsolidated VIEs	491		476
Investment In Funds [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Carrying Value of the Firm's Variable Interests in Nonconsolidated VIEs - Assets	409		413
Investment In Funds [Member] | Commitments and Guarantees, Maximum Exposure to Loss [Member]
Variable Interest Entity [Line Items]
Maximum Exposure to Loss in Nonconsolidated VIEs	79		60
Investment In Funds [Member] | Derivatives, Maximum Exposure to Loss [Member]
Variable Interest Entity [Line Items]
Maximum Exposure to Loss in Nonconsolidated VIEs	3		3
Investment In Funds [Member] | Debt and equity, Maximum Exposure to Loss [Member]
Variable Interest Entity [Line Items]
Maximum Exposure to Loss in Nonconsolidated VIEs	$ 409		$ 413