Bank Loans and Related Allowance for Credit Losses - Convert to Amortizing Loans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 40,477	$ 40,578
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	26,632	25,795
HELOCs
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	479	597
HELOCs | Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Converted to an amortizing loan by period end	168
Within 1 year	18
> 1 year – 3 years	41
> 3 years – 5 years	47
> 5 years	205
Total loans	479	$ 597
Converted to amortizing loans during the period	$ 21