Debt (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Long term debt and capital lease obligations
Current		$ 23,265		$ 23,265		$ 22,746
Debt		277,873		277,873		272,751
Finance Lease, Interest Expense		927	$ 1,210	2,852	$ 3,459
Interest paid on Senior Notes due 2024		3,378	3,563	10,134	10,907
Interest paid on Revolving Credit Facility		767	963	2,520	4,769
Amortization of Debt Issuance Costs		372	378	1,143	1,110
Accretion		0	182	0	541
Interest Expense, Other		45	58	261	60
Interest Costs Capitalized Adjustment		393	374	921	1,587
Interest Costs Incurred		5,096	5,980	15,989	19,259
Interest expenses incurred for various debt instruments
Interest paid on Senior Notes due 2024		3,378	3,563	10,134	10,907
Interest paid on Revolving Credit Facility		767	963	2,520	4,769
Amortization of Debt Issuance Costs		372	378	1,143	1,110
Accretion		0	182	0	541
Interest Expense, Other		45	58	261	60
Capitalized interest		(393)	(374)	(921)	(1,587)
Total interest expense, net of capitalized interest		5,096	$ 5,980	15,989	$ 19,259
Revolving Credit Facility
Long term debt and capital lease obligations
Debt	[1]	20,000		20,000		0
Senior Notes due 2024
Long term debt and capital lease obligations
Debt	[2]	227,414		227,414		226,885
Capital Lease Obligations
Long term debt and capital lease obligations
Debt						45,866
Debt, non-current		30,459		30,459		45,866
Revolving Credit Facility
Long term debt and capital lease obligations
Current	[1]	0		0		0
Senior Notes due 2024
Long term debt and capital lease obligations
Current	[2]	0		0		0
Capital Lease Obligations
Long term debt and capital lease obligations
Current		23,265		23,265		$ 22,746
Revolving Credit Facility
Long term debt and capital lease obligations
Debt		$ 20,000		$ 20,000
Stated interest rate		2.70%		2.70%

[1] Unamortized debt issuance costs of $1.7 million and $2.3 million at September 30, 2020 and December 31, 2019, respectively, included in Other Non-Current Assets.

[2] Net of unamortized debt issuance costs of $2.6 million and $3.1 million at September 30, 2020 and December 31, 2019, respectively.