Annual report pursuant to Section 13 and 15(d)

Commitments - Schedule of Firm Sales Contracted with Third Parties (Details)

v3.8.0.1
Commitments - Schedule of Firm Sales Contracted with Third Parties (Details)
Dec. 31, 2017
MMBTU
Commitments and Contingencies Disclosure [Abstract]  
2018 560,800
2019 659,000
2020 526,000
2021 372,000
2022 272,000
Thereafter 240,000
Total 2,629,800