Bank Loans and Related Allowance for Credit Losses - Composition of Bank Loans and Delinquency Analysis by Loan Segment (Details) - USD ($)		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Past Due [Line Items]
Total loans		$ 40,477,000,000	$ 40,578,000,000
Allowance for credit losses		38,000,000	73,000,000	$ 18,000,000	$ 30,000,000
Total bank loans – net	[1]	40,439,000,000	40,505,000,000
Loans accruing interest contractually 90 days or more past due		0	0
Current
Financing Receivable, Past Due [Line Items]
Total loans		40,414,000,000	40,522,000,000
Total past due and other nonaccrual loans
Financing Receivable, Past Due [Line Items]
Total loans		63,000,000	56,000,000
30-59 days past due
Financing Receivable, Past Due [Line Items]
Total loans		45,000,000	31,000,000
60-89 days past due
Financing Receivable, Past Due [Line Items]
Total loans		3,000,000	2,000,000
>90 days past due and other nonaccrual loans
Financing Receivable, Past Due [Line Items]
Total loans		15,000,000	23,000,000
Residential real estate
Financing Receivable, Past Due [Line Items]
Total loans		26,632,000,000	25,795,000,000
Allowance for credit losses		34,000,000	70,000,000	15,000,000	27,000,000
Total bank loans – net		26,598,000,000	25,725,000,000
Unamortized premiums and discounts and direct origination costs		$ 100,000,000	$ 98,000,000
Residential real estate | Loans Geographic Area | California | Geographic Concentration Risk
Financing Receivable, Past Due [Line Items]
Concentration risk percentage		43.00%	43.00%
Residential real estate | Current
Financing Receivable, Past Due [Line Items]
Total loans		$ 26,584,000,000	$ 25,747,000,000
Residential real estate | Total past due and other nonaccrual loans
Financing Receivable, Past Due [Line Items]
Total loans		48,000,000	48,000,000
Residential real estate | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Total loans		34,000,000	27,000,000
Residential real estate | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Total loans		3,000,000	2,000,000
Residential real estate | >90 days past due and other nonaccrual loans
Financing Receivable, Past Due [Line Items]
Total loans		11,000,000	19,000,000
Pledged asset lines
Financing Receivable, Past Due [Line Items]
Total loans		13,548,000,000	14,592,000,000
Allowance for credit losses		0	0	0	0
Total bank loans – net		13,548,000,000	14,592,000,000
Pledged asset lines | Current
Financing Receivable, Past Due [Line Items]
Total loans		13,533,000,000	14,584,000,000
Pledged asset lines | Total past due and other nonaccrual loans
Financing Receivable, Past Due [Line Items]
Total loans		15,000,000	8,000,000
Pledged asset lines | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Total loans		11,000,000	4,000,000
Pledged asset lines | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Total loans		0	0
Pledged asset lines | >90 days past due and other nonaccrual loans
Financing Receivable, Past Due [Line Items]
Total loans		4,000,000	4,000,000
Other
Financing Receivable, Past Due [Line Items]
Total loans		297,000,000	191,000,000
Allowance for credit losses		4,000,000	3,000,000	3,000,000	3,000,000
Total bank loans – net		293,000,000	188,000,000
Other | Current
Financing Receivable, Past Due [Line Items]
Total loans		297,000,000	191,000,000
Other | Total past due and other nonaccrual loans
Financing Receivable, Past Due [Line Items]
Total loans		0	0
Other | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Total loans		0	0
Other | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Total loans		0	0
Other | >90 days past due and other nonaccrual loans
Financing Receivable, Past Due [Line Items]
Total loans		0	0
First Mortgages
Financing Receivable, Past Due [Line Items]
Total loans		26,153,000,000	25,198,000,000
First Mortgages | Residential real estate
Financing Receivable, Past Due [Line Items]
Total loans		26,153,000,000	25,198,000,000
Allowance for credit losses		32,000,000	66,000,000	13,000,000	22,000,000
Total bank loans – net		26,121,000,000	25,132,000,000
First Mortgages | Residential real estate | Current
Financing Receivable, Past Due [Line Items]
Total loans		26,111,000,000	25,157,000,000
First Mortgages | Residential real estate | Total past due and other nonaccrual loans
Financing Receivable, Past Due [Line Items]
Total loans		42,000,000	41,000,000
First Mortgages | Residential real estate | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Total loans		33,000,000	25,000,000
First Mortgages | Residential real estate | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Total loans		2,000,000	2,000,000
First Mortgages | Residential real estate | >90 days past due and other nonaccrual loans
Financing Receivable, Past Due [Line Items]
Total loans		7,000,000	14,000,000
HELOCs
Financing Receivable, Past Due [Line Items]
Total loans		479,000,000	597,000,000
HELOCs | Residential real estate
Financing Receivable, Past Due [Line Items]
Total loans		479,000,000	597,000,000
Allowance for credit losses		2,000,000	4,000,000	$ 2,000,000	$ 5,000,000
Total bank loans – net		477,000,000	593,000,000
HELOCs | Residential real estate | Current
Financing Receivable, Past Due [Line Items]
Total loans		473,000,000	590,000,000
HELOCs | Residential real estate | Total past due and other nonaccrual loans
Financing Receivable, Past Due [Line Items]
Total loans		6,000,000	7,000,000
HELOCs | Residential real estate | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Total loans		1,000,000	2,000,000
HELOCs | Residential real estate | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Total loans		1,000,000	0
HELOCs | Residential real estate | >90 days past due and other nonaccrual loans
Financing Receivable, Past Due [Line Items]
Total loans		$ 4,000,000	$ 5,000,000

[1] Certain prior year amounts have been reclassified to conform to the current year presentation. See Note 1 for additional information.