Loans and asset quality - Nonperforming Assets (Details) - Domestic - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Impaired [Line Items]
With an allowance	$ 69
Without an allowance	18
Total nonperforming loans	87	$ 86
With an allowance, Other assets owned	1
Without an allowance, Other assets owned	0
Other assets owned	1	3
With an allowance, Total nonperforming assets	70
Without an allowance, Total nonperforming assets	18
Total nonperforming assets	88	89
Other residential mortgages
Financing Receivable, Impaired [Line Items]
With an allowance	60
Without an allowance	0
Total nonperforming loans	60	62
Wealth management loans and mortgages
Financing Receivable, Impaired [Line Items]
With an allowance	9
Without an allowance	18
Total nonperforming loans	$ 27	$ 24