Loans and asset quality - Nonperforming Assets (Details) - Domestic - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Financing Receivable, Impaired [Line Items]
With an allowance	$ 66
Without an allowance	17
Total nonperforming loans	83	$ 86
With an allowance, Other assets owned	0
Without an allowance, Other assets owned	1
Other assets owned	1	3
With an allowance, Total nonperforming assets	66
Without an allowance, Total nonperforming assets	18
Total nonperforming assets	84	89
Other residential mortgages
Financing Receivable, Impaired [Line Items]
With an allowance	56
Without an allowance	0
Total nonperforming loans	56	62
Wealth management loans and mortgages
Financing Receivable, Impaired [Line Items]
With an allowance	10
Without an allowance	17
Total nonperforming loans	$ 27	$ 24