Business Segments Additional Information (Details) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2018 segment	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment		5
Other Revenues under the Group Reporting Basis [Member]
Segment Reporting Information [Line Items]
Gains (losses) from the fair value movement on structured notes and deposits attributable to our own credit spread	$ 26		$ (23)
IFRS 9 [Member] | Group Reporting Basis [Member] | Retained Earnings [Member]
Segment Reporting Information [Line Items]
Cumulative effect of new accounting principle in period of adoption				$ (60)
IFRS 9 [Member] | Group Reporting Basis [Member] | Customer Loan Allowance for ECL [Member]
Segment Reporting Information [Line Items]
Cumulative effect of new accounting principle in period of adoption				$ 60