Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020		Mar. 31, 2019	Dec. 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		$ 37			$ 41
Revaluation period		90 days
Deferred fees		$ 3			2
Derivative financial assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets		628		$ 288
Derivative financial liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 liabilities	[1]	546		242
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets		679		870	703		$ 2,088
Fair value of level 3 liabilities		1,024		1,402	1,128		1,337
Fair Value Assets, Transfers Into Level 3		0		0
Fair Value Assets, Transfers Out of Level 3		0		1
Fair Value Liability, Transfers Into Level 3		0		0
Fair Value Liability, Transfers Out of Level 3		37		69
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]	0		1
Unfunded Loan Commitment [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Deferred fees		157			162
Deposits [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 liabilities	[1]	653	[3],[4]	949	774	[3],[4]	925
Fair Value Liability, Transfers Into Level 3	[1]	0		0
Fair Value Liability, Transfers Out of Level 3	[1]	33		61
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]	371	[3],[4]	453	354	[3],[4]	412
Fair Value Liability, Transfers Into Level 3	[1]	0		0
Fair Value Liability, Transfers Out of Level 3	[1]	4		8
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]			90			100
Fair Value Assets, Transfers Into Level 3	[5]			0
Fair Value Assets, Transfers Out of Level 3	[5]			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		16	[5]	16	$ 17	[5]	16
Fair Value Assets, Transfers Into Level 3		0		0
Fair Value Assets, Transfers Out of Level 3		$ 0	[5]	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				95			$ 92
Fair Value Assets, Transfers Into Level 3				0
Fair Value Assets, Transfers Out of Level 3				$ 0

[1] Excluding unrealized gains (losses) on fair value option liabilities attributable to our own credit spread, which are recorded in other comprehensive income, gains (losses) on fair value option liabilities are included in 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 $628 million and derivative liabilities of $546 million at March 31, 2020 and derivative assets of $288 million and derivative liabilities of $242 million at March 31, 2019. Gains (losses) on derivatives, net are predominantly included in trading revenue and 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).