Debt - Revolving Credit Facility (Details) - USD ($) $ in Thousands	1 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Aug. 31, 2016	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2018	Jun. 30, 2017	May 31, 2017
Debt instruments
Long-term debt				$ 53,828	$ 53,464
Remaining amount available to borrow				0
Repayment of outstanding debt	$ 28,900	$ 41,400
Revolving credit facility
Debt instruments
Maximum borrowing capacity	55,000	85,000	$ 150,000			$ 200,000
Additional borrowing capacity							$ 25,000	$ 25,000
Outstanding borrowings in long term debt				54,678	54,678
Remaining amount available to borrow				0	0
Incurred deferred financing costs	$ 800	$ 900	$ 500
Unamortized deferred financing costs				900	1,200
Letter of credit
Debt instruments
Outstanding borrowings in long term debt				$ 300	$ 300