Business Segments - Summary on Reconciliation of Results Under Ifrs to Us Gaap (Detail) - USD ($) $ in Millions		3 Months Ended										12 Months Ended
		Dec. 31, 2019		Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018		Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Operating Statistics [Line Items]
Net Interest Income												$ 2,303		$ 2,559		$ 2,387
Group Reporting Basis Other operating income												1,537		1,604		1,727
Group Reporting Basis Total operating income												3,840		4,163		4,114
Expected credit losses/provision for credit losses												171		(199)		(119)
Group Reporting Basis Revenues												3,669		4,362		4,233
Operating Expenses												3,313		3,633		3,333
Group Reporting Basis Profit (Loss) Before Income Tax Expense												356		729		900
Total Assets		$ 214,223					$ 203,375					214,223		203,375		220,313
Group Reporting Basis Total loans, net		66,449					67,040					66,449		67,040		68,215
Group Reporting Basis Goodwill		1,051					1,260					1,051		1,260		1,260
Group Reporting Basis Total deposits		103,589					97,371					103,589		97,371		97,294
Net interest income		507		$ 503	$ 540	$ 562	586		$ 559	$ 555	$ 552	2,112		2,252		2,273
Other operating income		542		486	436	390	363		486	537	513	1,854	[1]	1,899	[1]	2,002	[1]
Total operating income												3,966		4,151		4,275
Provision for credit losses		(3)		94	46	58	23		20	(45)	(71)	195		(73)		(165)
Total income												3,771		4,224		4,440
Operating expenses		871		1,106	774	750	780		790	786	1,282	3,501		3,638		3,391
Income before income tax		181		$ (211)	$ 156	$ 144	146		$ 235	$ 351	$ (146)	270		586		1,049
Total assets		175,375	[2]				172,448	[2]				175,375	[2]	172,448	[2]	187,235
Total loans, net		67,916					68,437					67,916		68,437		71,882
Goodwill		1,242					1,607					1,242		1,607		1,607
Total deposits		119,693					110,955					119,693		110,955		118,702
Group Reporting Basis Adjustments [Member]
Operating Statistics [Line Items]
Net Interest Income	[3]											13		(16)		(48)
Group Reporting Basis Other operating income	[3]											102		(9)		200
Group Reporting Basis Total operating income	[3]											115		(25)		152
Expected credit losses/provision for credit losses	[3]											32		115		(72)
Group Reporting Basis Revenues	[3]											83		(140)		224
Operating Expenses	[3]											169		3		75
Group Reporting Basis Profit (Loss) Before Income Tax Expense	[3]											(86)		(143)		149
Total Assets	[3]	(38,848)					(30,927)					(38,848)		(30,927)		(33,078)
Group Reporting Basis Total loans, net	[3]	(2,965)					(2,428)					(2,965)		(2,428)		(1,397)
Group Reporting Basis Goodwill	[3]	191					347					191		347		347
Group Reporting Basis Total deposits	[3]	(4,747)					(2,017)					(4,747)		(2,017)		(3,261)
Group Reporting Basis Reclassifications [Member]
Operating Statistics [Line Items]
Net Interest Income	[4]											(204)		(291)		(66)
Group Reporting Basis Other operating income	[4]											215		304		75
Group Reporting Basis Total operating income	[4]											11		13		9
Expected credit losses/provision for credit losses	[4]											(8)		11		26
Group Reporting Basis Revenues	[4]											19		2		(17)
Operating Expenses	[4]											19		2		(17)
Group Reporting Basis Profit (Loss) Before Income Tax Expense	[4]											0		0		0
Total Assets	[4]	0					0					0		0		0
Group Reporting Basis Total loans, net	[4]	4,432					3,825					4,432		3,825		5,064
Group Reporting Basis Goodwill	[4]	0					0					0		0		0
Group Reporting Basis Total deposits	[4]	20,851					15,601					20,851		15,601		24,669
RBWM [Member]
Operating Statistics [Line Items]
Goodwill							737							737
RBWM [Member] | Operating Segments [Member]
Operating Statistics [Line Items]
Net Interest Income												843		889		886
Group Reporting Basis Other operating income												225		297		526
Group Reporting Basis Total operating income												1,068		1,186		1,412
Expected credit losses/provision for credit losses												114		38		25
Group Reporting Basis Revenues												954		1,148		1,387
Operating Expenses												1,419		1,286		1,185
Group Reporting Basis Profit (Loss) Before Income Tax Expense												(465)		(138)		202
Total Assets		19,429					19,000					19,429		19,000		18,707
Group Reporting Basis Total loans, net		17,639					16,918					17,639		16,918		16,685
Group Reporting Basis Goodwill		372					581					372		581		581
Group Reporting Basis Total deposits		37,009					32,612					37,009		32,612		34,186
CMB [Member] | Operating Segments [Member]
Operating Statistics [Line Items]
Net Interest Income												815		797		739
Group Reporting Basis Other operating income												226		226		216
Group Reporting Basis Total operating income												1,041		1,023		955
Expected credit losses/provision for credit losses												55		(43)		(52)
Group Reporting Basis Revenues												986		1,066		1,007
Operating Expenses												576		589		558
Group Reporting Basis Profit (Loss) Before Income Tax Expense												410		477		449
Total Assets		25,737					25,047					25,737		25,047		23,644
Group Reporting Basis Total loans, net		24,465					23,913					24,465		23,913		22,444
Group Reporting Basis Goodwill		358					358					358		358		358
Group Reporting Basis Total deposits		29,632					23,604					29,632		23,604		24,239
GB&M [Member] | Operating Segments [Member]
Operating Statistics [Line Items]
Net Interest Income												458		610		585
Group Reporting Basis Other operating income												840		751		617
Group Reporting Basis Total operating income												1,298		1,361		1,202
Expected credit losses/provision for credit losses												1		(194)		(94)
Group Reporting Basis Revenues												1,297		1,555		1,296
Operating Expenses												825		834		881
Group Reporting Basis Profit (Loss) Before Income Tax Expense												472		721		415
Total Assets		88,440					73,187					88,440		73,187		72,734
Group Reporting Basis Total loans, net		16,740					18,895					16,740		18,895		19,125
Group Reporting Basis Goodwill		0					0					0		0		0
Group Reporting Basis Total deposits		27,605					30,181					27,605		30,181		25,476
PB [Member] | Operating Segments [Member]
Operating Statistics [Line Items]
Net Interest Income												136		172		217
Group Reporting Basis Other operating income												68		73		94
Group Reporting Basis Total operating income												204		245		311
Expected credit losses/provision for credit losses												1		(4)		2
Group Reporting Basis Revenues												203		249		309
Operating Expenses												212		236		244
Group Reporting Basis Profit (Loss) Before Income Tax Expense												(9)		13		65
Total Assets		7,326					6,797					7,326		6,797		8,190
Group Reporting Basis Total loans, net		6,089					5,715					6,089		5,715		6,405
Group Reporting Basis Goodwill		321					321					321		321		321
Group Reporting Basis Total deposits		6,539					8,193					6,539		8,193		8,470
CC [Member] | Operating Segments [Member]
Operating Statistics [Line Items]
Net Interest Income												51		91		(40)
Group Reporting Basis Other operating income												178		257		274
Group Reporting Basis Total operating income												229		348		234
Expected credit losses/provision for credit losses												0		4		0
Group Reporting Basis Revenues												229		344		234
Operating Expenses												281		688		465
Group Reporting Basis Profit (Loss) Before Income Tax Expense												(52)		(344)		(231)
Total Assets		73,291					79,344					73,291		79,344		97,038
Group Reporting Basis Total loans, net		1,516					1,599					1,516		1,599		3,556
Group Reporting Basis Goodwill		0					0					0		0		0
Group Reporting Basis Total deposits		$ 2,804					$ 2,781					$ 2,804		$ 2,781		$ 4,923

[1] See Note 24, "Business Segments," for a reconciliation of total other revenues on a U.S. GAAP basis to other operating income for each business segment under the Group Reporting Basis.

[2] The following table summarizes assets and liabilities related to our consolidated variable interest entities ("VIEs") at December 31, 2019 and December 31, 2018 which are consolidated on our balance sheet. Assets and liabilities exclude intercompany balances that eliminate in consolidation. See Note 17, "Variable Interest Entities," for additional information. Assets: Other assets $98 million and $112 million. Total assets $98 million and $112 million respectively. Liabilities: Long-term debt $0 million and $66 million, Interest, taxes and other liabilities $38 million and $37 million. Total liabilities $38 million and $103 million, respectively.

[3] 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:

[4] Represents differences in financial statement presentation between U.S. GAAP and the Group Reporting Basis.