Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Jun. 30, 2020		Jun. 30, 2019		Jun. 30, 2020		Jun. 30, 2019		Mar. 31, 2020	Dec. 31, 2019		Mar. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Unfunded commitments, equity securities measured at net asset value		$ 36				$ 36					$ 41
Revaluation period						90 days
Deferred fees		3				$ 3					2
Derivative financial assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets		534		$ 276		534		$ 276
Derivative financial liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 liabilities	[1]	413		194		413		194
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets		754		898		754		898		$ 653	703		$ 867	$ 2,088
Fair value of level 3 liabilities		1,019		1,371		1,019		1,371		998	1,128		1,402	1,337
Fair Value Assets, Transfers Into Level 3		8		0		8		0
Fair Value Assets, Transfers Out of Level 3		1		(7)		2		(6)
Fair Value Liability, Transfers Into Level 3		0		5		0		5
Fair Value Liability, Transfers Out of Level 3		28		81		64		150
Level 3 [Member] | Equity contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivatives, net, Transfers out of Level 3	[2]	1		(2)		2		(1)
Unfunded Loan Commitment [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Deferred fees		155				155					162
Deposits [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 liabilities	[1]	672	[3],[4]	930		672	[3],[4]	930		678	774	[3],[4]	949	925
Fair Value Liability, Transfers Into Level 3	[1]	0		5		0		5
Fair Value Liability, Transfers Out of Level 3	[1]	15		42		48		103
Long-term debt [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 liabilities	[1]	347	[3],[4]	441		347	[3],[4]	441		320	354	[3],[4]	453	412
Fair Value Liability, Transfers Into Level 3	[1]	0		0		0		0
Fair Value Liability, Transfers Out of Level 3	[1]	13		39		16		47
Collateralized debt obligations [Member] | Level 3 [Member] | Trading assets, excluding derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets	[5]			86				86					90	100
Fair Value Assets, Transfers Into Level 3	[5]			0				0
Fair Value Assets, Transfers Out of Level 3	[5]			0				0
Residential mortgage asset-backed securities [Member] | Level 3 [Member] | Trading assets, excluding derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets	[5]	15		16		15		16		$ 16	$ 17		16	16
Fair Value Assets, Transfers Into Level 3		0	[5]	0	[5]	0		0	[5]
Fair Value Assets, Transfers Out of Level 3	[5]	$ 0		0		$ 0		0
Student loan asset-backed securities [Member] | Level 3 [Member] | Trading assets, excluding derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets	[5]			90				90					$ 95	$ 92
Fair Value Assets, Transfers Into Level 3	[5]			0				0
Fair Value Assets, Transfers Out of Level 3	[5]			$ 0				$ 0

[1] Excluding unrealized gains (losses) on fair value option liabilities attributable to our own credit spread, which are recorded in other comprehensive income (loss), gains (losses) on fair value option liabilities are included in gain (loss) on instruments designated at fair value and related derivatives in the consolidated statement of income (loss).

[2] Level 3 net derivatives included derivative assets of $534 million and derivative liabilities of $413 million at June 30, 2020 and derivative assets of $276 million and derivative liabilities of $194 million at June 30, 2019. Gains (losses) on derivatives, net are predominantly included in trading revenue and gain (loss) on instruments designated at fair value and related derivatives in the consolidated statement of income (loss).

[3] Structured deposits and structured notes contain embedded derivative features whose fair value measurements contain significant Level 3 inputs. See equity and foreign exchange derivatives below for a discussion of the uncertainty of Level 3 inputs related to structured deposits and structured notes.

[4] We are the client-facing entity and we enter into identical but opposite derivatives to transfer the resultant risks to our affiliates. With the exception of counterparty credit risks, we are market neutral. The corresponding intra-group derivatives are presented as equity derivatives and foreign exchange derivatives in the table.

[5] Gains (losses) on trading assets, excluding derivatives are included in trading revenue in the consolidated statement of income (loss).