Commitments and Contingencies - Schedule of Volume Commitments (Details)
Jun. 30, 2018
MMBTU
Total Volume Commitments (MMBtu)  
2018 22,300,000
2019 116,800,000
2020 194,800,000
2021 158,100,000
2022 19,700,000
Total Volume Commitments (MMBtu) 511,700,000
Volume (MMBtu/d)  
2018 121,500
2019 320,000
2020 533,600
2021 433,200
2022 64,800