Selected Quarterly Financial Data (Details) - USD ($) $ in Millions	3 Months Ended									12 Months Ended
	Dec. 31, 2018		Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Condensed Income Statements, Captions [Line Items]
Net interest income	$ 586		$ 559	$ 555	$ 552	$ 534	$ 560	$ 582	$ 597	$ 2,252		$ 2,273		$ 2,484
Provision for credit losses	23		20	(45)	(71)	(45)	(22)	(21)	(77)	(73)		(165)		372
Net interest income after provision for credit losses	563		539	600	623	579	582	603	674	2,325		2,438		2,112
Total other revenues	363		486	537	513	458	393	558	593	1,899	[1]	2,002	[1]	1,404	[1],[2]
Operating expenses	780		790	786	1,282	903	820	849	819	3,638	[1]	3,391	[1],[3]	3,298	[1],[3]
Income (loss) before income tax	146		235	351	(146)	134	155	312	448	586		1,049		218
Income tax expense (benefit)	34		58	82	92	907	61	108	152	266		1,228		89
Net income (loss)	112	[4]	$ 177	$ 269	$ (238)	$ (773)	$ 94	$ 204	$ 296	$ 320		$ (179)		$ 129
Out of Period Adjustments [Member]
Condensed Income Statements, Captions [Line Items]
Net income (loss)	56
Out of Period Adjustments, Prior Period Amounts [Member]
Condensed Income Statements, Captions [Line Items]
Net income (loss)	$ 33

[1] 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, 2018 Deposit incentives$9 $— $— $20 $(11) $(10)Derivatives— — — — — (30,866)Expected credit losses / loan impairment(6) — 118 — (124) (386)Goodwill— — — — — 347Loan origination(29) (3) — (14) (18) 45Loans held for sale9 6 (3) — 18 45Pension and other postretirement benefit costs— — — 8 (8) (44)Property— — — (8) 8 7Securities transferred to held-to-maturity— — — — — (76)Other1 (12) — (3) (8) 11Total adjustments$(16) $(9) $115 $3 $(143) $(30,927) December 31, 2017 Derivatives$— $— $— $— $— $(32,900)Expected credit losses / loan impairment(43) — (72) — 29 (332)Goodwill— (1) — — (1) 347Loan origination(19) — — (14) (5) 42Loans held for sale9 141 — — 150 21Pension and other postretirement benefit costs— — — 94 (94) (263)Property— — — (11) 11 8Structured notes and deposits— 85 — — 85 —Other5 (25) — 6 (26) (1)Total adjustments$(48) $200 $(72) $75 $149 $(33,078) December 31, 2016 Derivatives$— $— $— $— $— $(44,911)Expected credit losses / loan impairment(57) 7 (58) 1 7 (326)Goodwill— — — — — 348Loan origination(21) — — (19) (2) 35Loans held for sale— (80) (20) — (60) (31)Pension and other postretirement benefit costs— — — 19 (19) (191)Property— — — (19) 19 16Unquoted equity securities— — — — — (163)Other2 (31) — (8) (21) (11)Total adjustments$(76) $(104) $(78) $(26) $(76) $(45,234)

[2] See Note 23, "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.

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

[4] Fourth quarter 2018 reflects out of period adjustments which reduced net income by $56 million, $33 million of which relates to prior year periods. We concluded these adjustments were not material to the current and prior year periods.