Loans Held for Sale (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	$ 282	$ 289
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	193	212
Commercial Loans [Member] | Real Estate, Including Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	10	83
Commercial Loans [Member] | Business and Corporate Banking [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	0	35
Commercial Loans [Member] | Global Banking [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	183	94
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	89	77
Consumer Loans [Member] | Residential Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	$ 89	$ 77