Debt - Schedule of Amounts Borrowed Under Wells Fargo Revolving Credit Agreement (Details) - Wells Fargo Credit Agreement - Wells Fargo Revolving Credit Facility - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Line of Credit Facility [Line Items]
Average borrowings under Wells Fargo Revolving Credit Facility	$ 47,031	$ 26,662
Average Interest Cost on Wells Fargo Revolving Credit Facility	6.51%	6.85%
Accrued and unpaid interest	$ 174	$ 90
LIBOR
Line of Credit Facility [Line Items]
LIBOR loan interest rate	5.97%	4.51%
Prime Rate
Line of Credit Facility [Line Items]
Wells Fargo Prime Rate (Base Rate) loan interest rate	7.25%	6.00%