Loans Held for Sale (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	$ 337	$ 289
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	129	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	119	94
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	208	77
Consumer Loans [Member] | Residential Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	$ 208	$ 77