Impacts of Derivative Financial Instruments on the Consolidated Statements of Income/(Loss) and the Consolidated Statements of Shareholders' Equity (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 201		$ 440		$ 311
Mortgage Servicing Income [Member] | Mortgage Servicing Rights [Member]
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	42		62		19
Other Trading [Member] | Other Trading [Member]
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	42		51		61
Other Trading [Member] | Foreign Exchange Contract [Member]
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments	(37)		101		93
Other Trading [Member] | Credit Risk Contract [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	26		19		23
Other Trading [Member] | Equity Contract [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net			4		4
Other Trading [Member] | Commodity Contract [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	1		3		2
Other Income [Member] | Loans Held For Investment [Member]
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments			(1)		(1)
Other Income [Member] | Credit Risk Contract [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(4)		(3)		(1)
Mortgage Production Income [Member] | Loans Held For Sale [Member]
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	(54)		(6)		(45)
Mortgage Production Income [Member] | Other Contract [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	185		210		156
Cash Flow Hedging [Member] | Interest Income [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	(54)	[1]	(145)	[2]	246	[3]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	38	[1]	147	[2]	169	[3]
Fair Value Hedging [Member] | Other Trading [Member]
Derivative, Gain (Loss) on Derivative, Net	(38)		(87)		(2)
Gain (Loss) on Fair Value Hedges Recognized in Earnings	40		89		1
Gain (Loss) on Fair Value Hedge Ineffectiveness, Net	2		2		(1)
Fair Value Hedging [Member] | Other Trading [Member] | Fixed Income Interest Rate [Member]
Derivative, Gain (Loss) on Derivative, Net	(38)	[4]	(87)	[5]	(2)	[6]
Gain (Loss) on Fair Value Hedges Recognized in Earnings	40	[4]	89	[5]	1	[6]
Gain (Loss) on Fair Value Hedge Ineffectiveness, Net	2	[4]	2	[5]	(1)	[6]
Fair Value Hedging [Member] | Other Trading [Member] | Brokered Time Deposits [Member]
Derivative, Gain (Loss) on Derivative, Net	0	[4]	0	[5]	0	[6]
Gain (Loss) on Fair Value Hedges Recognized in Earnings	0	[4]	0	[5]	0	[6]
Gain (Loss) on Fair Value Hedge Ineffectiveness, Net	$ 0	[4]	$ 0	[5]	$ 0	[6]

[1] During the year ended December 31, 2017, the Company also reclassified $51 million of pre-tax gains from AOCI into Net interest income relating to hedging relationships that have been terminated and are reclassified into earnings consistent with the pattern of net cash flows expected to be recognized.

[2] During the year ended December 31, 2016, the Company also reclassified $97 million of pre-tax gains from AOCI into Net interest income relating to hedging relationships that have been terminated and are reclassified into earnings consistent with the pattern of net cash flows expected to be recognized.

[3] During the year ended December 31, 2015, the Company also reclassified $92 million pre-tax gains from AOCI into Net interest income relating to hedging relationships that have been terminated and are reclassified into earnings consistent with the pattern of net cash flows expected to be recognized.

[4] Amounts are recognized in Trading income in the Consolidated Statements of Income.

[5] Amounts are recognized in Trading income in the Consolidated Statements of Income.

[6] Amounts are recognized in Trading income in the Consolidated Statements of Income.