Bank Loans and Related Allowance for Loan Losses (Narrative) (Details) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017 USD ($) loan	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) loan	Jun. 30, 2016 USD ($)	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	$ 9,200		$ 9,200		$ 8,400
Commitments to purchase First Mortgage loans			$ 457		$ 466
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	$ 30		$ 30		$ 31
Impaired assets, which include nonaccrual loans, other real estate owned and troubled debt restructurings	41		41		45
Secured by second liens	15,843		15,843		15,429
Adjustable Rate First Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Bank loans	8,600		$ 8,600
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
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			48.00%		48.00%
First Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchased first mortgages and HELOCs	683	$ 691	$ 1,300	$ 1,200
Home Equity Loans and Lines of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchased first mortgages and HELOCs	111	$ 112	$ 229	$ 222
Loan term			30 years
Initial draw period			10 years
Converting to amortizing loans period			20 years
Secured by second liens	$ 2,148		$ 2,148		$ 2,350
Percent of minimum interest paid	38.00%		38.00%
Home Equity Secured By Second Liens [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Secured by second liens	$ 1,700		$ 1,700