Bank Loans and Related Allowance for Credit Losses - Convert to Amortizing Loans (Details) - Residential real estate - HELOCs - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Converted to an amortizing loan by period end	$ 156
Within 1 year	17
> 1 year – 3 years	38
> 3 years – 5 years	44
> 5 years	200
Total loans	455	$ 479
Converted to amortizing loans during the period	$ 3