Business Segments - Summary on Reconciliation of Results Under Ifrs to Us Gaap (Detail) - USD ($) $ in Millions		3 Months Ended										12 Months Ended
		Dec. 31, 2017		Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016		Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Operating Statistics [Line Items]
Group Reporting Basis Net interest income	[1]											$ 2,387		$ 2,471		$ 2,317
Group Reporting Basis Other operating income	[2]											1,727		1,595		2,010
Group Reporting Basis Total operating income												4,114		4,066		4,327
Group Reporting Basis Loan impairment charges												(119)		494		264
Group Reporting Basis Revenues												4,233		3,572		4,063
Group Reporting Basis Operating expenses	[2]											3,333		3,278	[3]	3,308	[3]
Group Reporting Basis Profit (Loss) Before Income Tax Expense												900		294		755
Group Reporting Basis Total assets		$ 220,313					$ 246,506					220,313		246,506		234,530
Group Reporting Basis Total loans, net		68,215					72,464					68,215		72,464		78,214
Group Reporting Basis Goodwill		1,260					1,264					1,260		1,264		1,264
Group Reporting Basis Total deposits		97,294					95,344					97,294		95,344		94,145
Net interest income		534		$ 560	$ 582	$ 597	588		$ 604	$ 638	$ 654	2,273	[1]	2,484	[1]	2,470	[1]
Other operating income		458		393	558	593	282		338	307	477	2,002	[2]	1,404	[2]	1,735	[2]
Total operating income												4,275		3,888		4,205
Loan impairment charges		(45)		(22)	(21)	(77)	19		62	134	157	(165)		372	[4]	361
Total income												4,440		3,516		3,844
Operating expenses		903		820	849	819	899		821	837	741	3,391	[2]	3,298	[2],[3]	3,284	[2],[3]
Income before income tax		134		$ 155	$ 312	$ 448	(48)		$ 59	$ (26)	$ 233	1,049		218		560
Total assets		187,235	[5]				201,301	[5]				187,235	[5]	201,301	[5]	188,278
Total loans, net		71,882					72,858					71,882		72,858		82,005
Goodwill		1,607					1,612					1,607		1,612		1,612
Total deposits		118,702					129,248					118,702		129,248		118,579
Group Reporting Basis Adjustments [Member]
Operating Statistics [Line Items]
Group Reporting Basis Net interest income	[1],[6]											(48)		(76)		(78)
Group Reporting Basis Other operating income	[2],[6]											200		(104)		(39)
Group Reporting Basis Total operating income	[6]											152		(180)		(117)
Group Reporting Basis Loan impairment charges	[6]											(72)		(78)		130
Group Reporting Basis Revenues	[6]											224		(102)		(247)
Group Reporting Basis Operating expenses	[2],[6]											75		(26)	[3]	(52)	[3]
Group Reporting Basis Profit (Loss) Before Income Tax Expense	[6]											149		(76)		(195)
Group Reporting Basis Total assets	[6]	(33,078)					(45,234)					(33,078)		(45,234)		(46,569)
Group Reporting Basis Total loans, net	[6]	(1,397)					(405)					(1,397)		(405)		317
Group Reporting Basis Goodwill	[6]	347					348					347		348		348
Group Reporting Basis Total deposits	[6]	(3,261)					(4,379)					(3,261)		(4,379)		(4,097)
Group Reporting Basis Reclassifications [Member]
Operating Statistics [Line Items]
Group Reporting Basis Net interest income	[1]											(66)		89		231
Group Reporting Basis Other operating income	[2]											75		(87)		(236)
Group Reporting Basis Total operating income												9		2		(5)
Group Reporting Basis Loan impairment charges												26		(44)		(33)
Group Reporting Basis Revenues												(17)		46		28
Group Reporting Basis Operating expenses	[2]											(17)		46	[3]	28	[3]
Group Reporting Basis Profit (Loss) Before Income Tax Expense												0		0		0
Group Reporting Basis Total assets		0					29					0		29		317
Group Reporting Basis Total loans, net		5,064					799					5,064		799		3,474
Group Reporting Basis Goodwill		0					0					0		0		0
Group Reporting Basis Total deposits		24,669					38,283					24,669		38,283		28,531
Reclassification [Member]
Operating Statistics [Line Items]
Group Reporting Basis Net interest income	[1]											0		(2)		(12)
Group Reporting Basis Other operating income	[2]											0		2		12
Group Reporting Basis Total operating income												0		0		0
Group Reporting Basis Loan impairment charges												0		0		0
Group Reporting Basis Revenues												0		0		0
Group Reporting Basis Operating expenses	[2]											0		0	[3]	0	[3]
Group Reporting Basis Profit (Loss) Before Income Tax Expense												0		0		0
Group Reporting Basis Total assets		0					0					0		0		0
Group Reporting Basis Total loans, net		0					0					0		0		0
Group Reporting Basis Goodwill		0					0					0		0		0
Group Reporting Basis Total deposits		0					0					0		0		0
RBWM [Member] | Operating Segments [Member]
Operating Statistics [Line Items]
Group Reporting Basis Net interest income	[1]											886		818		787
Group Reporting Basis Other operating income	[2]											526		363		308
Group Reporting Basis Total operating income												1,412		1,181		1,095
Group Reporting Basis Loan impairment charges												25		70		68
Group Reporting Basis Revenues												1,387		1,111		1,027
Group Reporting Basis Operating expenses	[2]											1,185		1,131	[3]	1,152	[3]
Group Reporting Basis Profit (Loss) Before Income Tax Expense												202		(20)		(125)
Group Reporting Basis Total assets		18,707					19,618					18,707		19,618		19,700
Group Reporting Basis Total loans, net		16,685					16,889					16,685		16,889		16,696
Group Reporting Basis Goodwill		581					581					581		581		581
Group Reporting Basis Total deposits		34,186					32,472					34,186		32,472		31,814
Increase (decrease) in segment profit before tax during the year ended December 31:														7		(4)
Increase (decrease) in segment total deposits at December 31:														0		0
RBWM [Member] | Operating Segments [Member] | Restatement Adjustment [Member]
Operating Statistics [Line Items]
Group Reporting Basis Other operating income														11
Group Reporting Basis Operating expenses														11
CMB [Member] | Operating Segments [Member]
Operating Statistics [Line Items]
Group Reporting Basis Net interest income	[1]											739		749		747
Group Reporting Basis Other operating income	[2]											216		229		243
Group Reporting Basis Total operating income												955		978		990
Group Reporting Basis Loan impairment charges												(52)		50		140
Group Reporting Basis Revenues												1,007		928		850
Group Reporting Basis Operating expenses	[2]											558		591	[3]	609	[3]
Group Reporting Basis Profit (Loss) Before Income Tax Expense												449		337	[6]	241
Group Reporting Basis Total assets		23,644					25,082					23,644		25,082		26,763
Group Reporting Basis Total loans, net		22,444					24,125					22,444		24,125		23,538
Group Reporting Basis Goodwill		358					358					358		358		358
Group Reporting Basis Total deposits		24,239					22,005					24,239		22,005		20,599
Increase (decrease) in segment profit before tax during the year ended December 31:														13		8
Increase (decrease) in segment total deposits at December 31:														0		0
GBM [Member] | Operating Segments [Member]
Operating Statistics [Line Items]
Group Reporting Basis Net interest income	[1]											585		567		409
Group Reporting Basis Other operating income	[2]											617		785		1,047
Group Reporting Basis Total operating income												1,202		1,352		1,456
Group Reporting Basis Loan impairment charges												(94)		383		65
Group Reporting Basis Revenues												1,296		969		1,391
Group Reporting Basis Operating expenses	[2]											881		986	[3]	1,017	[3]
Group Reporting Basis Profit (Loss) Before Income Tax Expense												415		(17)	[6]	374
Group Reporting Basis Total assets		72,734					85,215					72,734		85,215		99,360
Group Reporting Basis Total loans, net		19,125					21,914					19,125		21,914		29,589
Group Reporting Basis Goodwill		0					0					0		0		0
Group Reporting Basis Total deposits		25,476					22,260					25,476		22,260		22,910
Increase (decrease) in segment profit before tax during the year ended December 31:														(192)		(144)
Increase (decrease) in segment total deposits at December 31:														(6,989)		(5,011)
GBM [Member] | Operating Segments [Member] | Restatement Adjustment [Member]
Operating Statistics [Line Items]
Group Reporting Basis Other operating income														61		63
Group Reporting Basis Operating expenses														61		63
PB [Member] | Operating Segments [Member]
Operating Statistics [Line Items]
Group Reporting Basis Net interest income	[1]											217		207		205
Group Reporting Basis Other operating income	[2]											94		89		99
Group Reporting Basis Total operating income												311		296		304
Group Reporting Basis Loan impairment charges												2		0		(5)
Group Reporting Basis Revenues												309		296		309
Group Reporting Basis Operating expenses	[2]											244		232	[3]	245	[3]
Group Reporting Basis Profit (Loss) Before Income Tax Expense												65		64		64
Group Reporting Basis Total assets		8,190					7,714					8,190		7,714		8,428
Group Reporting Basis Total loans, net		6,405					6,024					6,405		6,024		6,715
Group Reporting Basis Goodwill		321					325					321		325		325
Group Reporting Basis Total deposits		8,470					11,618					8,470		11,618		13,811
Increase (decrease) in segment profit before tax during the year ended December 31:														5		4
Increase (decrease) in segment total deposits at December 31:														0		0
CC [Member] | Operating Segments [Member]
Operating Statistics [Line Items]
Group Reporting Basis Net interest income	[1]											(40)		132		181
Group Reporting Basis Other operating income	[2]											274		127		301
Group Reporting Basis Total operating income												234		259		482
Group Reporting Basis Loan impairment charges												0		(9)		(4)
Group Reporting Basis Revenues												234		268		486
Group Reporting Basis Operating expenses	[2]											465		338	[3]	285	[3]
Group Reporting Basis Profit (Loss) Before Income Tax Expense												(231)		(70)		201
Group Reporting Basis Total assets		97,038					108,877					97,038		108,877		80,279
Group Reporting Basis Total loans, net		3,556					3,512					3,556		3,512		1,676
Group Reporting Basis Goodwill		0					0					0		0		0
Group Reporting Basis Total deposits		$ 4,923					$ 6,989					$ 4,923		6,989		5,011
Increase (decrease) in segment profit before tax during the year ended December 31:														167		136
Increase (decrease) in segment total deposits at December 31:														$ 6,989		$ 5,011

[1] Net interest income of each segment represents the difference between actual interest earned on assets and interest paid on liabilities of the segment adjusted for a funding charge or credit. Segments are charged a cost to fund assets (e.g. customer loans) and receive a funding credit for funds provided (e.g. customer deposits) based on equivalent market rates. The objective of these charges/credits is to transfer interest rate risk from the segments to one centralized unit in Balance Sheet Management and more appropriately reflect the profitability of the segments.

[2] Expenses for the segments include fully apportioned corporate overhead expenses.

[3] In 2017, we changed our presentation for certain cost reimbursements that were previously netted as an offset to affiliate expense. We now present these reimbursements gross in affiliate income. As a result, we have reclassified prior year amounts in order to conform to the current year presentation, which increased both RBWM other operating income and RBWM operating expenses $11 million during the year ended December 31, 2016 and also increased both GB&M other operating income and GB&M operating expenses $61 million and $63 million during the years ended December 31, 2016 and 2015, respectively. See Note 21, "Related Party Transactions," in the accompanying consolidated financial statements for additional information.

[4] The provision for credit losses and charge-offs for residential mortgage loans during 2016 includes $11 million related to the lower of amortized cost or fair value adjustment attributable to credit factors for loans transferred to held for sale. See Note 7, "Loans Held for Sale," for additional information.

[5] The following table summarizes assets and liabilities related to our consolidated variable interest entities ("VIEs") at December 31, 2017 and December 31, 2016 which are consolidated on our balance sheet. Assets and liabilities exclude intercompany balances that eliminate in consolidation. See Note 24, "Variable Interest Entities," for additional information. Assets: Other assets $154 million and $231 million. Total assets $154 million and $231 million respectively. Liabilities: Long-term debt $73 million and $79 million, Interest, taxes and other liabilities $59 million and $60 million. Total liabilities $132 million and $139 million, respectively.

[6] Represents adjustments associated with differences between U.S. GAAP and the Group Reporting Basis. These adjustments, which are more fully described above, consist of the following: NetInterestIncome OtherRevenues Provisionfor CreditLosses OperatingExpenses Profit (Loss)before IncomeTax Expense TotalAssets (in millions)December 31, 2017 Derivatives$— $— $— $— $— $(32,900)Goodwill— (1) — — (1) 347Litigation— — — 8 (8) —Loan impairment(43) — (72) — 29 (332)Loan origination(19) — — (14) (5) 42Loans held for sale9 141 — — 150 21Low income housing tax credit investments— (7) — — (7) —Pension and other postretirement benefit costs— — — 94 (94) (263)Property— — — (11) 11 8Structured notes and deposits— 85 — — 85 —Other5 (18) — (2) (11) (1)Total adjustments$(48) $200 $(72) $75 $149 $(33,078) December 31, 2016 Derivatives$— $— $— $— $— $(44,911)Goodwill— — — — — 348Litigation— — — (8) 8 (3)Loan impairment(57) 7 (58) 1 7 (326)Loan origination(21) — — (19) (2) 35Loans held for sale— (80) (20) — (60) (31)Low income housing tax credit investments— (9) — — (9) —Pension and other postretirement benefit costs— — — 19 (19) (191)Property— — — (19) 19 16Unquoted equity securities— — — — — (163)Other2 (22) — — (20) (8)Total adjustments$(76) $(104) $(78) $(26) $(76) $(45,234) December 31, 2015 Derivatives$— $(3) $— $— $(3) $(46,245)Goodwill— — — — — 348Litigation— — — (2) 2 —Loan impairment(61) 3 132 1 (191) (329)Loan origination(22) (3) — (47) 22 49Loans held for sale— (16) (2) — (14) (4)Low income housing tax credit investments— (12) — — (12) —Pension and other postretirement benefit costs— — — 15 (15) (177)Property— — — (19) 19 21Unquoted equity securities— — — — — (228)Other5 (8) — — (3) (4)Total adjustments$(78) $(39) $130 $(52) $(195) $(46,569)