Fair Value (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Level 1
Fair Value of Financial Instruments
Net derivative asset (liability)	$ 0	$ 0
Level 2
Fair Value of Financial Instruments
Net derivative asset (liability)	(1,047)	(527)
Level 3
Fair Value of Financial Instruments
Net derivative asset (liability)	0	0
Commodity futures natural gas contracts | Level 1
Fair Value of Financial Instruments
Net derivative asset (liability)	0	0
Commodity futures natural gas contracts | Level 2
Fair Value of Financial Instruments
Net derivative asset (liability)	(99)	1,508
Commodity futures natural gas contracts | Level 3
Fair Value of Financial Instruments
Net derivative asset (liability)	0	0
Interest Rate Swap | Level 1
Fair Value of Financial Instruments
Net derivative asset (liability)	0	0
Interest Rate Swap | Level 2
Fair Value of Financial Instruments
Net derivative asset (liability)	(948)	(2,035)
Interest Rate Swap | Level 3
Fair Value of Financial Instruments
Net derivative asset (liability)	0	0
Total
Fair Value of Financial Instruments
Net derivative asset (liability)	(1,047)	(527)
Total | Commodity futures natural gas contracts
Fair Value of Financial Instruments
Net derivative asset (liability)	(99)	1,508
Total | Interest Rate Swap
Fair Value of Financial Instruments
Net derivative asset (liability)	$ (948)	$ (2,035)