Summary of Significant Accounting Policies and New Accounting Pronouncements Charge-off and Nonaccrual Policies and Practices (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 payment	Dec. 31, 2015 USD ($)
Financing Receivable, Allowance for Credit Losses [Line Items]
Delinquency threshold for loss reserves	90 days
Reduction to REO expense | $		$ 7
Consumer Loan [Member] | Residential Mortgage [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Period of consecutive payments	3 months
Delinquent threshold period for write-offs	6 months
Nonaccrual status delinquent threshold period	3 months
Number of qualifying payments to resume accrual of interest | payment	6
Broker price opinion or appraisals number of days	180 days
Number of days valuation is determined	90 days