Purchased Receivables - Summary of Components of Net Purchased Receivables (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Purchased Receivables [Abstract]
Purchased receivables	$ 21,427	$ 14,596
Reserve for purchased receivable losses	(141)	(190)
Total	$ 21,286	$ 14,406