Debt - Components of Interest Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Line of Credit Facility [Line Items]
Letters of credit fees and commitment fees	$ 1,472	$ 1,656	$ 1,604
Amortization of deferred financing costs	1,210	1,275	1,291
Interest expense	5,266	8,621	9,410
Senior Credit Facility
Line of Credit Facility [Line Items]
Interest incurred on long-term debt	2,291	5,263	5,300
Other
Line of Credit Facility [Line Items]
Interest incurred on long-term debt	293	197	26
Promissory Note
Line of Credit Facility [Line Items]
Interest incurred on long-term debt	$ 0	$ 230	$ 1,189