Fair Value Measurements - Quantitative Information about Recurring Fair Value Measurement of Assets and Liabilities Classified as Level 3 (Detail) $ in Millions		9 Months Ended	12 Months Ended
		Sep. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)
Level 3 [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Assets, Fair Value Disclosure, Recurring		$ 2,347	$ 3,564
Liabilities, Fair Value Disclosure, Recurring		(1,667)	(2,114)
Level 1 [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Assets, Fair Value Disclosure, Recurring		27,172	28,846
Liabilities, Fair Value Disclosure, Recurring		(1,547)	(1,163)
Collateralized debt obligations [Member] | Level 3 [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Assets, Fair Value Disclosure, Recurring		$ 125	$ 184
Collateralized debt obligations [Member] | Recurring [Member] | Broker quotes or consensus pricing and, where applicable, discounted cash flows [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Inputs, Loss Severity		85.00%	85.00%
Collateralized debt obligations [Member] | Recurring [Member] | Minimum [Member] | Broker quotes or consensus pricing and, where applicable, discounted cash flows [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Inputs, Prepayment Rate		1.00%	1.00%
Fair Value Inputs, Probability of Default		6.00%	6.00%
Collateralized debt obligations [Member] | Recurring [Member] | Maximum [Member] | Broker quotes or consensus pricing and, where applicable, discounted cash flows [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Inputs, Prepayment Rate		6.00%	6.00%
Fair Value Inputs, Probability of Default		8.00%	8.00%
Corporate and other domestic debt securities [Member] | Level 3 [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Assets, Fair Value Disclosure, Recurring		$ 1,803	$ 2,884
Corporate and other domestic debt securities [Member] | Recurring [Member] | Discounted cash flows [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Inputs, Correlation Between Insurance Claim Shortfall and Collateral Value		80.00%	80.00%
Corporate and other domestic debt securities [Member] | Recurring [Member] | Minimum [Member] | Discounted cash flows [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Inputs, Spread Volatility on Collateral Assets		2.00%	3.00%
Corporate and other domestic debt securities [Member] | Recurring [Member] | Maximum [Member] | Discounted cash flows [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Inputs, Spread Volatility on Collateral Assets		4.00%	4.00%
Other securities [Member] | Level 3 [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Assets, Fair Value Disclosure, Recurring		$ 110	$ 105
Other securities [Member] | Recurring [Member] | Minimum [Member] | Discounted cash flows [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Inputs, Comparability Adjustments		1.00%	1.00%
Other securities [Member] | Recurring [Member] | Maximum [Member] | Discounted cash flows [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Inputs, Comparability Adjustments		3.00%	4.00%
Credit contracts [Member] | Level 3 [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Assets, Fair Value Disclosure, Recurring		$ 115	$ 193
Credit contracts [Member] | Recurring [Member] | Minimum [Member] | Option pricing model [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Inputs, Issuer by Issuer Correlation of Defaults		82.00%	82.00%
Fair Value Inputs, Credit Default Swap Spreads		1.81%	1.50%
Credit contracts [Member] | Recurring [Member] | Maximum [Member] | Option pricing model [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Inputs, Issuer by Issuer Correlation of Defaults		83.00%	83.00%
Fair Value Inputs, Credit Default Swap Spreads		1.99%	1.73%
Equity contracts [Member] | Level 3 [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Assets, Fair Value Disclosure, Recurring	[1]	$ 56	$ (2)
Equity contracts [Member] | Recurring [Member] | Minimum [Member] | Option pricing model [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Inputs, Equity/Equity Index Volatility	[1]	7.00%	11.00%
Fair Value Inputs, Equity/Equity and Equity/Index Correlation	[1]	44.00%	45.00%
Fair Value Inputs, Equity Dividend Yields	[1]	0.00%	0.00%
Equity contracts [Member] | Recurring [Member] | Maximum [Member] | Option pricing model [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Inputs, Equity/Equity Index Volatility	[1]	43.00%	49.00%
Fair Value Inputs, Equity/Equity and Equity/Index Correlation	[1]	80.00%	57.00%
Fair Value Inputs, Equity Dividend Yields	[1]	9.00%	14.00%
Foreign exchange contracts [Member] | Level 3 [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Assets, Fair Value Disclosure, Recurring	[1]	$ 0	$ 0
Foreign exchange contracts [Member] | Recurring [Member] | Minimum [Member] | Option pricing model [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Inputs, Implied Volatility Currency Pairs	[1]	8.00%	15.00%
Foreign exchange contracts [Member] | Recurring [Member] | Maximum [Member] | Option pricing model [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Inputs, Implied Volatility Currency Pairs	[1]	12.00%	21.00%
Interest rate contracts [Member] | Level 3 [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Assets, Fair Value Disclosure, Recurring		$ 0	$ 1
Interest rate contracts [Member] | Recurring [Member] | Minimum [Member] | Market comparable adjusted for probability to fund [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Inputs, Probability to Fund for Rate Lock Commitments		38.00%	38.00%
Interest rate contracts [Member] | Recurring [Member] | Maximum [Member] | Market comparable adjusted for probability to fund [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Inputs, Probability to Fund for Rate Lock Commitments		100.00%	100.00%
Other Contract [Member] | Level 3 [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Assets, Fair Value Disclosure, Recurring		$ (46)	$ (9)
Other Contract [Member] | Recurring [Member] | Discounted cash flows [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Inputs, Conversion Rate		1.6	1.6
Other Contract [Member] | Recurring [Member] | Minimum [Member] | Discounted cash flows [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Inputs, Expected Duration		2 years	3 years
Other Contract [Member] | Recurring [Member] | Maximum [Member] | Discounted cash flows [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Inputs, Expected Duration		5 years	5 years
Domestic Deposits [Member] | Level 3 [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Liabilities, Fair Value Disclosure, Recurring	[1],[2]	$ (945)	$ (1,407)
Domestic Deposits [Member] | Recurring [Member] | Minimum [Member] | Option adjusted discounted cash flows [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Inputs, Implied Volatility Currency Pairs	[1],[2]	8.00%	15.00%
Fair Value Inputs, Equity/Equity Index Volatility	[1],[2]	7.00%	11.00%
Fair Value Inputs, Equity/Equity and Equity/Index Correlation		44.00%	45.00%
Domestic Deposits [Member] | Recurring [Member] | Maximum [Member] | Option adjusted discounted cash flows [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Inputs, Implied Volatility Currency Pairs	[1],[2]	12.00%	21.00%
Fair Value Inputs, Equity/Equity Index Volatility	[1],[2]	43.00%	49.00%
Fair Value Inputs, Equity/Equity and Equity/Index Correlation		80.00%	57.00%
Long-term debt [Member] | Level 3 [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Liabilities, Fair Value Disclosure, Recurring	[1],[2]	$ (553)	$ (499)
Long-term debt [Member] | Recurring [Member] | Minimum [Member] | Option adjusted discounted cash flows [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Inputs, Implied Volatility Currency Pairs	[1],[2]	8.00%	15.00%
Fair Value Inputs, Equity/Equity Index Volatility	[1],[2]	7.00%	11.00%
Fair Value Inputs, Equity/Equity and Equity/Index Correlation	[1],[2]	44.00%	45.00%
Long-term debt [Member] | Recurring [Member] | Maximum [Member] | Option adjusted discounted cash flows [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Inputs, Implied Volatility Currency Pairs	[1],[2]	12.00%	21.00%
Fair Value Inputs, Equity/Equity Index Volatility	[1],[2]	43.00%	49.00%
Fair Value Inputs, Equity/Equity and Equity/Index Correlation	[1],[2]	80.00%	57.00%
Other assets [Member] | Level 3 [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Assets, Fair Value Disclosure, Recurring	[3]	$ 15
Other assets [Member] | Level 1 [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Assets, Fair Value Disclosure, Recurring	[3]	$ 0
Other assets [Member] | Recurring [Member] | Minimum [Member] | Discounted cash flows [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Inputs, Client Transfer Rate		50.00%
Other assets [Member] | Recurring [Member] | Maximum [Member] | Discounted cash flows [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Inputs, Client Transfer Rate		95.00%

[1] 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.

[2] Structured deposits and structured notes contain embedded derivative features whose fair value measurements contain significant Level 3 inputs.

[3] Represents contingent consideration receivable associated with the sale of a portion of our Private Banking business.