Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value, Assets, Level 2 to Level 1 Transfers, Amount		$ 0	$ 0
Average deviation of implied volatility, foreign currency pair		1.00%
Average deviation of implied volatility, at-the-money equity option		5.00%
Revaluation period		45 days
Derivative Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets		$ 301	391
Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 liabilities	[1]	$ 152	208
Residential Mortgage [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value Inputs, Loss Severity		69.00%
Impaired commercial loans [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value Inputs, Loss Severity		29.00%
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets		$ 2,207	3,356	$ 3,328
Fair value of level 3 liabilities		1,538	1,906	2,613
Fair Value Assets, Transfers Into Level 3		4	106
Fair Value Assets, Transfers Out of Level 3		1	(92)
Fair Value Liability, Transfers Into Level 3		43	55
Fair Value Liability, Transfers Out of Level 3		362	453
Level 3 [Member] | Mortgage servicing rights [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets	[2]		0	140
Fair Value Assets, Transfers Into Level 3	[2]		0
Fair Value Assets, Transfers Out of Level 3	[2]		(96)
Level 3 [Member] | Domestic Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 liabilities	[1]	897	1,407	1,867
Fair Value Liability, Transfers Into Level 3	[1]	31	55
Fair Value Liability, Transfers Out of Level 3	[1]	260	212
Level 3 [Member] | Borrowings [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 liabilities	[1]	641	499	746
Fair Value Liability, Transfers Into Level 3	[1]	12	0
Fair Value Liability, Transfers Out of Level 3	[1]	102	241
Other asset-backed securities available-for-sale [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets	[3]	111	105	$ 0
Fair Value Assets, Transfers Into Level 3	[3]	0	105
Fair Value Assets, Transfers Out of Level 3	[3]	0	0
Unfunded Loan Commitment [Member] | Standby Letters of Credit [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Deferred fees on commitments and standby letters of credit		$ 158	$ 49

[1] See Note 15, "Fair Value Option," for additional information. Beginning January 1, 2017, unrealized gains (losses) on fair value option liabilities attributable to our own credit spread is recorded in other comprehensive income (loss).

[2] During the fourth quarter of 2016, we sold our remaining residential mortgage servicing rights portfolio to a third party. Gains (losses) on residential mortgage servicing rights were included in residential mortgage banking revenue (expense) in the consolidated statement of income (loss).

[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 (loss).