Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Unfunded commitments, equity securities measured at net asset value		$ 41		$ 72
Revaluation period		90 days
Deferred fees		$ 2		2
Derivative financial assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets		287		179
Derivative financial liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 liabilities	[1]	222		213
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets		703		2,088		$ 2,207
Fair value of level 3 liabilities		1,128		1,337		1,538
Fair Value Assets, Transfers Into Level 3		(17)		106
Fair Value Assets, Transfers Out of Level 3		(152)		21
Fair Value Liability, Transfers Into Level 3		7		29
Fair Value Liability, Transfers Out of Level 3		341		365
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		21
Unfunded Loan Commitment [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Deferred fees		162		165
Deposits [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 liabilities	[1]	774	[3],[4]	925	[3],[4]	897
Fair Value Liability, Transfers Into Level 3	[1]	7		28
Fair Value Liability, Transfers Out of Level 3	[1]	223		206
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]	354	[3],[4]	412	[3],[4]	641
Fair Value Liability, Transfers Into Level 3	[1]	0		1
Fair Value Liability, Transfers Out of Level 3	[1]	118		159
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]	0		100		129
Fair Value Assets, Transfers Into Level 3	[5]	0		0
Fair Value Assets, Transfers Out of Level 3	[5]	(72)		0
Residential Mortgage 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		17	[5]	16	[5]	0
Fair Value Assets, Transfers Into Level 3		0		16
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		0		92		$ 0
Fair Value Assets, Transfers Into Level 3		0		92
Fair Value Assets, Transfers Out of Level 3		$ (80)	[5]	$ 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 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 $287 million and derivative liabilities of $222 million at December 31, 2019 and derivative assets of $179 million and derivative liabilities of $213 million at December 31, 2018. 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).