Business Segments - Summary on Reconciliation of Results Under Ifrs to Us Gaap (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020		Mar. 31, 2019	Dec. 31, 2019
Operating Statistics [Line Items]
Net Interest Income		$ 519		$ 624
Group Reporting Basis Other operating income		371		338
Group Reporting Basis Total operating income		890		962
Expected credit losses / provision for credit losses		379
Expected credit losses/provision for credit losses				10
Group Reporting Basis Revenues		511		952
Operating Expenses		1,509		748
Group Reporting Basis Profit (Loss) Before Income Tax		(998)		204
Total Assets		269,609		209,645
Group Reporting Basis Total loans, net		78,655		69,214
Group Reporting Basis Goodwill		358		1,260
Group Reporting Basis Total deposits		124,315		98,225
Net interest income		504		562
Other operating income	[1]	387		390
Total operating income		891		952
Provision for credit losses		726
Provision for credit losses		512		58
Total income		165		894
Operating expenses		1,605		750
Income (loss) before income tax		(1,440)		144
Total assets		205,077	[2]	180,921	$ 175,375	[2]
Total loans, net		80,797		70,451	67,916
Goodwill		458		1,607	1,242
Total deposits		136,723		113,639	$ 119,693
Group Reporting Basis Adjustments [Member]
Operating Statistics [Line Items]
Net Interest Income	[3]	3		6
Group Reporting Basis Other operating income	[3]	(4)		(17)
Group Reporting Basis Total operating income	[3]	(1)		(11)
Expected credit losses / provision for credit losses	[3]	347
Expected credit losses/provision for credit losses	[3]			41
Group Reporting Basis Revenues	[3]	(348)		(52)
Operating Expenses	[3]	94		8
Group Reporting Basis Profit (Loss) Before Income Tax	[3]	(442)		(60)
Total Assets	[3]	(64,532)		(28,724)
Group Reporting Basis Total loans, net	[3]	(4,596)		(1,797)
Group Reporting Basis Goodwill	[3]	100		347
Group Reporting Basis Total deposits	[3]	(7,066)		(2,827)
Group Reporting Basis Reclassifications [Member]
Operating Statistics [Line Items]
Net Interest Income	[4]	(18)		(68)
Group Reporting Basis Other operating income	[4]	20		69
Group Reporting Basis Total operating income	[4]	2		1
Expected credit losses / provision for credit losses	[4]	0
Expected credit losses/provision for credit losses	[4]			7
Group Reporting Basis Revenues	[4]	2		(6)
Operating Expenses	[4]	2		(6)
Group Reporting Basis Profit (Loss) Before Income Tax	[4]	0		0
Total Assets	[4]	0		0
Group Reporting Basis Total loans, net	[4]	6,738		3,034
Group Reporting Basis Goodwill	[4]	0		0
Group Reporting Basis Total deposits	[4]	19,474		18,241
RBWM [Member] | Operating Segments [Member]
Operating Statistics [Line Items]
Net Interest Income		195		221
Group Reporting Basis Other operating income		59		65
Group Reporting Basis Total operating income		254		286
Expected credit losses / provision for credit losses		140
Expected credit losses/provision for credit losses				21
Group Reporting Basis Revenues		114		265
Operating Expenses		660		311
Group Reporting Basis Profit (Loss) Before Income Tax		(546)		(46)
Total Assets		18,954		18,733
Group Reporting Basis Total loans, net		17,701		16,885
Group Reporting Basis Goodwill		0		581
Group Reporting Basis Total deposits		39,083		33,459
CMB [Member] | Operating Segments [Member]
Operating Statistics [Line Items]
Net Interest Income		208		201
Group Reporting Basis Other operating income		58		58
Group Reporting Basis Total operating income		266		259
Expected credit losses / provision for credit losses		123
Expected credit losses/provision for credit losses				6
Group Reporting Basis Revenues		143		253
Operating Expenses		146		138
Group Reporting Basis Profit (Loss) Before Income Tax		(3)		115
Total Assets		31,540		25,612
Group Reporting Basis Total loans, net		30,370		24,447
Group Reporting Basis Goodwill		358		358
Group Reporting Basis Total deposits		32,309		22,323
GB&M [Member] | Operating Segments [Member]
Operating Statistics [Line Items]
Net Interest Income		81		151
Group Reporting Basis Other operating income		264		175
Group Reporting Basis Total operating income		345		326
Expected credit losses / provision for credit losses		115
Expected credit losses/provision for credit losses				(17)
Group Reporting Basis Revenues		230		343
Operating Expenses		187		206
Group Reporting Basis Profit (Loss) Before Income Tax		43		137
Total Assets		114,802		78,899
Group Reporting Basis Total loans, net		22,461		20,068
Group Reporting Basis Goodwill		0		0
Group Reporting Basis Total deposits		40,417		28,274
PB [Member] | Operating Segments [Member]
Operating Statistics [Line Items]
Net Interest Income		31		37
Group Reporting Basis Other operating income		16		16
Group Reporting Basis Total operating income		47		53
Expected credit losses / provision for credit losses		0
Expected credit losses/provision for credit losses				(1)
Group Reporting Basis Revenues		47		54
Operating Expenses		370		53
Group Reporting Basis Profit (Loss) Before Income Tax		(323)		1
Total Assets		7,159		6,686
Group Reporting Basis Total loans, net		6,084		5,584
Group Reporting Basis Goodwill		0		321
Group Reporting Basis Total deposits		8,201		7,540
CC [Member] | Operating Segments [Member]
Operating Statistics [Line Items]
Net Interest Income		4		14
Group Reporting Basis Other operating income		(26)		24
Group Reporting Basis Total operating income		(22)		38
Expected credit losses / provision for credit losses		1
Expected credit losses/provision for credit losses				1
Group Reporting Basis Revenues		(23)		37
Operating Expenses		146		40
Group Reporting Basis Profit (Loss) Before Income Tax		(169)		(3)
Total Assets		97,154		79,715
Group Reporting Basis Total loans, net		2,039		2,230
Group Reporting Basis Goodwill		0		0
Group Reporting Basis Total deposits		$ 4,305		$ 6,629

[1] See Note 15, "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 March 31, 2020 and December 31, 2019 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: Loans $39 million and $0 million. Other assets $92 million and $98 million. Total assets $131 million and $98 million respectively. Liabilities: Interest, taxes and other liabilities $32 million and $38 million. Total liabilities $32 million and $38 million, respectively.

[3] Represents adjustments associated with differences between U.S. GAAP and the Group Reporting Basis.

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