Finance Receivables and Loans, Net Finance Receivables and Loans, Net (Commercial Concentration Risk) (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Concentration Risk [Line Items]
Commercial Concentration Risk	100.00%	100.00%
Texas
Concentration Risk [Line Items]
Commercial Concentration Risk	15.50%	15.70%
Florida
Concentration Risk [Line Items]
Commercial Concentration Risk	11.60%	10.30%
California
Concentration Risk [Line Items]
Commercial Concentration Risk	8.30%	8.20%
Michigan
Concentration Risk [Line Items]
Commercial Concentration Risk	6.80%	7.70%
New York
Concentration Risk [Line Items]
Commercial Concentration Risk	4.80%	2.10%
Georgia
Concentration Risk [Line Items]
Commercial Concentration Risk	4.00%	4.60%
North Carolina
Concentration Risk [Line Items]
Commercial Concentration Risk	3.60%	3.60%
South Carolina
Concentration Risk [Line Items]
Commercial Concentration Risk	3.40%	3.50%
New Jersey
Concentration Risk [Line Items]
Commercial Concentration Risk	3.10%	3.60%
Utah
Concentration Risk [Line Items]
Commercial Concentration Risk	2.60%	1.60%
United States, Other
Concentration Risk [Line Items]
Commercial Concentration Risk	36.30%	39.10%