Business and Summary of Significant Accounting Policies - Interest and Fees on Loans Receivable (Details)	12 Months Ended
	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Credit terms, merchant fee, percentage, promotional interest period one (in months)	6 months
Credit terms, merchant fee, percentage, promotional interest period two (in months)	12 months
Credit terms, merchant fee, percentage, promotional interest period three (in months)	18 months
Credit Card Loans1
Accounts, Notes, Loans and Financing Receivable [Line Items]
Credit terms, privilege period	24 months
Credit terms, minimum payment required, percentage of outstanding loan balance	3.50%
Credit Card Loans1 | Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Credit terms, merchant fee (percentage)	3.00%
Financing receivable promotional fees percent	1.00%
Credit terms, interest rate, fixed and variable (percentage)	17.90%
Credit Card Loans1 | Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Credit terms, merchant fee (percentage)	25.00%
Financing receivable promotional fees percent	7.90%
Credit terms, interest rate, fixed and variable (percentage)	29.99%