Loans - Loans by FICO Score, Consumer (Details) - Consumer	Mar. 31, 2019	Dec. 31, 2018
HELOC | FICO score 740 or greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	61.00%	61.40%
HELOC | FICO score 720-739
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	8.80%	8.50%
HELOC | FICO score 700-719
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	7.80%	7.60%
HELOC | FICO score 660-699
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	10.90%	10.90%
HELOC | FICO score 620-659
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	5.00%	5.10%
HELOC | FICO score less than 620
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	6.50%	6.50%
HELOC | Total
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	100.03812%	99.98%
R/E installment loans | FICO score 740 or greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	72.20%	71.30%
R/E installment loans | FICO score 720-739
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	8.30%	8.80%
R/E installment loans | FICO score 700-719
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	6.90%	7.00%
R/E installment loans | FICO score 660-699
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	7.20%	7.60%
R/E installment loans | FICO score 620-659
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	2.70%	2.80%
R/E installment loans | FICO score less than 620
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	2.70%	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)	52.00%	51.80%
Permanent mortgage | FICO score 720-739
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	8.30%	7.60%
Permanent mortgage | FICO score 700-719
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	9.90%	10.60%
Permanent mortgage | FICO score 660-699
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	14.80%	14.70%
Permanent mortgage | FICO score 620-659
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	7.00%	6.50%
Permanent mortgage | FICO score less than 620
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	8.00%	8.80%
Permanent mortgage | Total
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average refreshed FICO score (percent)	100.00%	100.00%