Purchased Receivables - Narrative (Details)	9 Months Ended
	Sep. 30, 2018 USD ($) segment purchased_receivable	Dec. 31, 2017 USD ($) purchased_receivable
Purchased Receivables [Abstract]
Term of purchased receivables (less than)	1 year
Number of classes of purchased receivables | segment	1
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured purchased receivables	$ 17,862,000	$ 23,800,000
Purchased Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of purchased receivables past due | purchased_receivable	0	0
Restructured purchased receivables	$ 0	$ 0