Loans (Loans by FICO Score, Consumer) (Details)	Mar. 31, 2018	Dec. 31, 2017
HELOC | FICO score 740 or greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	60.80%	60.00%
HELOC | FICO score 720-739
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	8.70%	8.70%
HELOC | FICO score 700-719
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	7.70%	8.30%
HELOC | FICO score 660-699
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	11.30%	11.10%
HELOC | FICO score 620-659
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	4.90%	4.90%
HELOC | FICO score less than 620
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	6.60%	7.00%
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)	73.50%	73.10%
R E Installment Loans | FICO score 720-739
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	7.70%	8.00%
R E Installment Loans | FICO score 700-719
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	6.00%	6.40%
R E Installment Loans | FICO score 660-699
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	7.60%	7.20%
R E Installment Loans | FICO score 620-659
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	2.80%	2.80%
R E Installment Loans | FICO score less than 620
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	2.40%	2.50%
R E Installment Loans | Total
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	100.00%	100.00%
Permanent Mortgage | FICO score 740 or greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	50.30%	46.40%
Permanent Mortgage | FICO score 720-739
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	10.10%	12.80%
Permanent Mortgage | FICO score 700-719
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	7.80%	9.20%
Permanent Mortgage | FICO score 660-699
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	14.20%	14.80%
Permanent Mortgage | FICO score 620-659
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	7.30%	7.30%
Permanent Mortgage | FICO score less than 620
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	10.30%	9.50%
Permanent Mortgage | Total
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	100.00%	100.00%