Bank Loans and Related Allowance for Loan Losses (Composition of Bank Loans and Delinquency Analysis by Loan Segment) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Past Due [Line Items]
Current	$ 18,173,000,000	$ 16,580,000,000
Past due and other nonaccrual loans	57,000,000	50,000,000
Total loans	18,230,000,000	16,630,000,000
Allowance for loan losses	18,000,000	21,000,000	$ 26,000,000	$ 26,000,000
Total bank loans – net	18,212,000,000	16,609,000,000
Loans accruing interest contractually 90 days or more past due	0	0
30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Past due and other nonaccrual loans	30,000,000	27,000,000
60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Past due and other nonaccrual loans	5,000,000	3,000,000
>90 Days Past Due And Other Nonaccrual Loans [Member]
Financing Receivable, Past Due [Line Items]
Past due and other nonaccrual loans	22,000,000	20,000,000
First Mortgage [Member]
Financing Receivable, Past Due [Line Items]
Current	11,665,000,000	10,349,000,000
Past due and other nonaccrual loans	39,000,000	35,000,000
Total loans	11,704,000,000	10,384,000,000
Allowance for loan losses	11,000,000	14,000,000	16,000,000	17,000,000
Total bank loans – net	11,693,000,000	10,370,000,000
First Mortgage [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Past due and other nonaccrual loans	24,000,000	21,000,000
First Mortgage [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Past due and other nonaccrual loans	4,000,000	2,000,000
First Mortgage [Member] | >90 Days Past Due And Other Nonaccrual Loans [Member]
Financing Receivable, Past Due [Line Items]
Past due and other nonaccrual loans	11,000,000	12,000,000
HELOC's [Member]
Financing Receivable, Past Due [Line Items]
Current	1,105,000,000	1,493,000,000
Past due and other nonaccrual loans	12,000,000	12,000,000
Total loans	1,117,000,000	1,505,000,000
Allowance for loan losses	4,000,000	5,000,000	8,000,000	8,000,000
Total bank loans – net	1,113,000,000	1,500,000,000
HELOC's [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Past due and other nonaccrual loans	2,000,000	3,000,000
HELOC's [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Past due and other nonaccrual loans	1,000,000	1,000,000
HELOC's [Member] | >90 Days Past Due And Other Nonaccrual Loans [Member]
Financing Receivable, Past Due [Line Items]
Past due and other nonaccrual loans	9,000,000	8,000,000
Pledged asset lines [Member]
Financing Receivable, Past Due [Line Items]
Current	5,202,000,000	4,558,000,000
Past due and other nonaccrual loans	4,000,000	3,000,000
Total loans	5,206,000,000	4,561,000,000
Allowance for loan losses	0	0
Total bank loans – net	5,206,000,000	4,561,000,000
Pledged asset lines [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Past due and other nonaccrual loans	4,000,000	3,000,000
Pledged asset lines [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Past due and other nonaccrual loans	0	0
Pledged asset lines [Member] | >90 Days Past Due And Other Nonaccrual Loans [Member]
Financing Receivable, Past Due [Line Items]
Past due and other nonaccrual loans	0	0
Other [Member]
Financing Receivable, Past Due [Line Items]
Current	201,000,000	180,000,000
Past due and other nonaccrual loans	2,000,000	0
Total loans	203,000,000	180,000,000
Allowance for loan losses	3,000,000	2,000,000	$ 2,000,000	$ 1,000,000
Total bank loans – net	200,000,000	178,000,000
Other [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Past due and other nonaccrual loans	0	0
Other [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Past due and other nonaccrual loans	0	0
Other [Member] | >90 Days Past Due And Other Nonaccrual Loans [Member]
Financing Receivable, Past Due [Line Items]
Past due and other nonaccrual loans	2,000,000	0
First Mortgage And Home Equity [Member]
Financing Receivable, Past Due [Line Items]
Unamortized premiums and discounts and direct origination costs	$ 74,000,000	$ 73,000,000
First Mortgage And Home Equity [Member] | California [Member] | Loans Geographic Area [Member]
Financing Receivable, Past Due [Line Items]
Concentration risk percentage	45.00%	47.00%