Loans (Loans by FICO Score, Consumer) (Details)	Sep. 30, 2017	Dec. 31, 2016
HELOC | FICO score 740 or greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	58.50%	56.90%
HELOC | FICO score 720-739
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	8.80%	8.80%
HELOC | FICO score 700-719
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	8.20%	8.60%
HELOC | FICO score 660-699
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	12.10%	13.20%
HELOC | FICO score 620-659
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	5.60%	5.60%
HELOC | FICO score less than 620
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	6.80%	6.90%
HELOC | Total
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	100.00%	100.00%
R E Installment Loans | FICO score 740 or greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	71.80%	70.30%
R E Installment Loans | FICO score 720-739
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	8.10%	8.30%
R E Installment Loans | FICO score 700-719
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	6.60%	6.80%
R E Installment Loans | FICO score 660-699
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	8.40%	8.40%
R E Installment Loans | FICO score 620-659
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	2.70%	3.50%
R E Installment Loans | FICO score less than 620
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	2.40%	2.70%
R E Installment Loans | Total
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	100.00%	100.00%
Permanent Mortgage Portfolio Segment | FICO score 740 or greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	45.10%	45.00%
Permanent Mortgage Portfolio Segment | FICO score 720-739
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	12.80%	9.50%
Permanent Mortgage Portfolio Segment | FICO score 700-719
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	11.00%	9.20%
Permanent Mortgage Portfolio Segment | FICO score 660-699
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	15.30%	17.10%
Permanent Mortgage Portfolio Segment | FICO score 620-659
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	7.00%	9.10%
Permanent Mortgage Portfolio Segment | FICO score less than 620
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	8.80%	10.10%
Permanent Mortgage Portfolio Segment | Total
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	100.00%	100.00%