Purchased Receivables - Summary of Allowance for Loan Losses Purchased Receivables (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	$ 171,000	$ 181,000	$ 289,000
Charge-offs	(1,744,000)	(1,482,000)	(826,000)
Balance at end of year	200,000	171,000	181,000
Purchased Receivable
Allowance for Loan and Lease Losses [Roll Forward]
Charge-offs	0	0	0
Recoveries	0	0	30,000
Net recoveries (charge-offs)	0	0	30,000
Reserve for (recovery from) purchased receivables	$ 29,000	$ (10,000)	$ (138,000)