Bank Loans and Related Allowance for Credit Losses - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrued interest	$ 157	$ 134
Total bank loans	40,477	40,578
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total bank loans	26,632	25,795
First Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total bank loans	26,153	25,198
First Mortgages | Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Bank loans	$ 21,500
Percent of loans with interest-only payments	27.00%
Percent of interest only adjustable rate	86.00%
Total bank loans	$ 26,153	25,198
First Mortgages | Minimum | Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fixed rate interest rate period	3 years
Interest-only reset period	3 years
First Mortgages | Maximum | Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fixed rate interest rate period	10 years
HELOCs
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total bank loans	$ 479	597
HELOCs | Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan term	30 years
Initial draw period	10 years
Converting to amortizing loan period	20 years
Total bank loans	$ 479	$ 597
Percent of loan balance outstanding, borrowers paid only minimum due	60.00%
Home Equity Secured By Second Liens | Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total bank loans	$ 379