Line of Credit (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Line of Credit Facility [Line Items]
Amount outstanding under line of credit	$ 78,000,000		$ 68,000,000
Interest expense on borrowings	$ 700,000	$ 1,300,000
Line of Credit | US Bank
Line of Credit Facility [Line Items]
Effective interest rate	2.20%
Line of Credit | US Bank | LIBOR | Minimum
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.25%
Line of Credit | US Bank | LIBOR | Maximum
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.75%
Line of Credit | US Bank | Base Rate | Minimum
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.00%
Line of Credit | US Bank | Base Rate | Maximum
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.50%
Line of Credit | US Bank | Enson
Line of Credit Facility [Line Items]
Ownership interest used to secure obligations	65.00%
Line of Credit | Second Amended Credit Agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 125,000,000
Commitment fees	0
Letter of Credit
Line of Credit Facility [Line Items]
Letter of credit outstanding amount	$ 2,700,000