Finance Receivables and Loans, Net Finance Receivables and Loans, Net (Commercial Concentration Risk) (Details)	Dec. 31, 2017	Dec. 31, 2016
Concentration Risk [Line Items]
Commercial Concentration Risk	100.00%	100.00%
TEXAS
Concentration Risk [Line Items]
Commercial Concentration Risk	15.70%	16.10%
FLORIDA
Concentration Risk [Line Items]
Commercial Concentration Risk	10.30%	10.20%
CALIFORNIA
Concentration Risk [Line Items]
Commercial Concentration Risk	8.20%	7.90%
MICHIGAN
Concentration Risk [Line Items]
Commercial Concentration Risk	7.70%	7.60%
GEORGIA
Concentration Risk [Line Items]
Commercial Concentration Risk	4.60%	3.60%
NEW JERSEY
Concentration Risk [Line Items]
Commercial Concentration Risk	3.60%	4.20%
NORTH CAROLINA
Concentration Risk [Line Items]
Commercial Concentration Risk	3.60%	3.60%
SOUTH CAROLINA
Concentration Risk [Line Items]
Commercial Concentration Risk	3.50%	2.70%
PENNSYLVANIA
Concentration Risk [Line Items]
Commercial Concentration Risk	3.00%	3.10%
MISSOURI
Concentration Risk [Line Items]
Commercial Concentration Risk	2.40%	2.50%
United States, Other
Concentration Risk [Line Items]
Commercial Concentration Risk	37.40%	38.50%