Fair Value Measurements - Additional Information (Detail) $ in Millions		3 Months Ended
		Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)		Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets		$ 3,351	$ 3,323		$ 3,356	$ 3,328
Fair value of level 3 liabilities		$ 1,774	2,495		1,906	2,613
Loss severity, trust preferred securities		0.85
Average deviation of implied volatility, foreign currency pair		2.00%
Average deviation of implied volatility, at-the-money equity option		5.00%
Fair Value Assets, Transfers Into Level 3		$ 0	1
Fair Value Assets, Transfers Out of Level 3		0	(1)
Fair Value Liability, Transfers Into Level 3		(5)	(8)
Fair Value Liability, Transfers Out of Level 3		$ 89	139
Revaluation period		45 days
Weighted Average [Member] | Residential mortgages and home equity mortgages [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value Inputs, Loss Severity		40.00%
Weighted Average [Member] | Impaired Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value Inputs, Loss Severity		34.00%
Derivative Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets		$ 343	391
Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 liabilities	[1]	167	268
Credit contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets	[2]	181	177		193	179
Fair Value Assets, Transfers Into Level 3	[2]	0	0
Fair Value Assets, Transfers Out of Level 3	[2]	0	0
Mortgage servicing rights [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets	[3]		117			140
Fair Value Assets, Transfers Into Level 3	[3]		0
Fair Value Assets, Transfers Out of Level 3	[3]		0
Domestic Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 liabilities		1,216	1,849	[1]	1,407	1,867	[1]
Fair Value Liability, Transfers Into Level 3	[1]	(3)	(8)
Fair Value Liability, Transfers Out of Level 3		46	55	[1]
Borrowings [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 liabilities		558	646	[1]	499	$ 746	[1]
Fair Value Liability, Transfers Into Level 3		(2)	0	[1]
Fair Value Liability, Transfers Out of Level 3		43	$ 84	[1]
Other liabilities [Member] | Standby Letters of Credit [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Deferred fees on standby letters of credit		$ 51			$ 49

[1] See Note 9, "Fair Value Option," for additional information. Beginning January 1, 2017, unrealized gains (losses) on fair value option liabilities attributable to credit spread is recorded in other comprehensive income.

[2] Level 3 net derivatives included derivative assets of $343 million and derivative liabilities of $167 million at March 31, 2017 and derivative assets of $391 million and derivative liabilities of $268 million at March 31, 2016. Gains (losses) on derivatives, net are predominantly included in trading revenue in the consolidated statement of income.

[3] Realized gains (losses) on securities available-for-sale are included in other securities gains, net in the consolidated statement income. Unrealized gains (losses) on securities available-for-sale are included in other comprehensive income.