Loans Mortgages With Potential Concentration of Credit Risk (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair Value, Concentration of Risk, Loans Receivable		$ 10,476	$ 11,421
Residential Mortgage Interest Only Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair Value, Concentration of Risk, Loans Receivable	[1]	2,110	4,053
Residential Mortgage Interest Only Loans [Member] | Mortgages With Mortgage Insurance or With LTV Ratio Less Than or Equal to 80% [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair Value, Concentration of Risk, Loans Receivable	[1]	1,563	3,180
Residential Mortgage Interest Only Loans [Member] | Mortgages With No Mortgage Insurance and With LTV Ratio Greater Than 80% [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair Value, Concentration of Risk, Loans Receivable	[1]	547	873
Residential Mortgage Amortizing Loans [Member] | Mortgages With LTV Ratio Greater Than 80% and/or second liens [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair Value, Concentration of Risk, Loans Receivable	[2]	$ 8,366	$ 7,368

[1] Comprised of first and/or second liens, primarily with an initial 10 year interest only period.

[2] Comprised of loans with no MI