Quarterly report pursuant to Section 13 or 15(d)

Commitments and Contingencies (Firm Transportation Commitments) (Details)

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Commitments and Contingencies (Firm Transportation Commitments) (Details)
$ in Thousands
Sep. 30, 2017
USD ($)
MMBTU
Other Commitments [Line Items]  
Remaining 2017 | MMBTU 710,000
2018 | MMBTU 561,000
2019 | MMBTU 659,000
2020 | MMBTU 526,000
2021 | MMBTU 372,000
Thereafter | MMBTU 249,000
Total | MMBTU 3,077,000
Transportation commitment  
Other Commitments [Line Items]  
Remaining 2017 $ 49,052
2018 238,767
2019 243,389
2020 240,746
2021 239,786
Thereafter 2,715,005
Total 3,726,745
Purchase commitment  
Other Commitments [Line Items]  
Remaining 2017 13,110
2018 39,330
Total $ 52,440