Purchased Receivables - Summary of Components of Net Purchased Receivables (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Purchased Receivables [Abstract]
Purchased receivables	$ 13,130		$ 20,662
Reserve for purchased receivable losses	(200)	$ (194)	(171)	$ (163)	$ (163)	$ (181)
Total	$ 12,930		$ 20,491