Bank Loans and Related Allowance for Loan Losses (Narrative) (Details) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017 USD ($) loan	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) loan	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($) loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commitments to extend credit related to unused HELOCs, PALs, and other lines of credit	$ 9,600		$ 9,600		$ 8,400
Number of loans accruing interest contractually 90 days or more past due | loan	0		0		0
Nonperforming assets, including nonaccrual loans and other real estate owned	$ 29		$ 29		$ 31
Impaired assets, which include nonaccrual loans, other real estate owned and troubled debt restructurings	38		38		45
Total bank loans	16,258		16,258		15,429
First Mortgage and Home Equity Loans and Lines of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unamortized premiums and discounts and direct origination costs	77		$ 77		$ 78
First Mortgage and Home Equity Loans and Lines of Credit [Member] | California [Member] | Loans, Geographic Area [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk percentage			47.00%		48.00%
First Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commitments to purchase First Mortgage loans			$ 459		$ 466
Purchased first mortgages and HELOCs	696	$ 858	2,000	$ 2,100
Home Equity Loans and Lines of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchased first mortgages and HELOCs	115	$ 93	$ 344	$ 315
Loan term			30 years
Initial draw period			10 years
Converting to amortizing loans period			20 years
Total bank loans	$ 2,042		$ 2,042		$ 2,350
Percent of minimum interest paid	39.00%		39.00%
Adjustable Rate First Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Bank loans	$ 8,800		$ 8,800
Percent of loans with interest-only payments			34.00%
Percent of interest only adjustable rate			56.00%
Adjustable Rate First Mortgage [Member] | Minimum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fixed rate interest rate period			3 years
Interest-only reset period			3 years
Adjustable Rate First Mortgage [Member] | Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fixed rate interest rate period			10 years
Home Equity Secured By Second Liens [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total bank loans	$ 1,600		$ 1,600