Debt (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Long term debt and capital lease obligations
Current		$ 22,074	$ 22,746
Debt		253,427	272,751
Finance Lease, Interest Expense		3,634	4,150	$ 2,270
Interest paid on Senior Notes due 2024		13,513	14,586	14,688
Interest paid on Revolving Credit Facility		3,165	5,358	5,854
Amortization of Debt Issuance Costs		1,525	1,491	1,302
Accretion		0	396	1,311
Interest Expense, Other		344	580	176
Interest Costs Capitalized Adjustment		1,473	1,790	1,237
Interest Costs Incurred		20,708	24,771	24,364
Interest expenses incurred for various debt instruments
Interest paid on Senior Notes due 2024		13,513	14,586	14,688
Interest paid on Revolving Credit Facility		3,165	5,358	5,854
Amortization of Debt Issuance Costs		1,525	1,491	1,302
Accretion		0	396	1,311
Interest Expense, Other		344	580	176
Capitalized interest		(1,473)	(1,790)	(1,237)
Total interest expense, net of capitalized interest		20,708	24,771	$ 24,364
Revolving Credit Facility
Long term debt and capital lease obligations
Debt	[1]	0	0
Senior Notes due 2024
Long term debt and capital lease obligations
Debt	[2]	227,590	226,885
Capital Lease Obligations
Long term debt and capital lease obligations
Debt			45,866
Debt, non-current		25,837	45,866
Revolving Credit Facility
Long term debt and capital lease obligations
Current	[1]	0	0
Senior Notes due 2024
Long term debt and capital lease obligations
Current	[2]	0	0
Capital Lease Obligations
Long term debt and capital lease obligations
Current		$ 22,074	$ 22,746
Revolving Credit Facility
Long term debt and capital lease obligations
Stated interest rate		2.40%

[1] Unamortized debt issuance costs of $1.5 million and $2.3 million at December 31, 2020 and December 31, 2019, respectively, included in Other Non-Current Assets.

[2] Net of unamortized debt issuance costs of $2.4 million and $3.1 million at December 31, 2020 and December 31, 2019, respectively.