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Related Party Transactions - Narrative (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2021 | Jun. 30, 2020 | Jun. 30, 2021 | Jun. 30, 2020
Black Warrior Methane (BWM) |  |  |  |
Related Party Transaction [Line Items] |  |  |  |
Proportionate consolidation method, ownership percentage | 50.00% |  | 50.00% |
Black Warrior Transmission (BWT) |  |  |  |
Related Party Transaction [Line Items] |  |  |  |
Equity method investment, ownership percentage | 50.00% |  | 50.00% |
Allocated Expenses to Joint Venture | Corporate Joint Venture |  |  |  |
Related Party Transaction [Line Items] |  |  |  |
Expenses from transactions with related party | $ 0.5 | $ 0.8 | $ 1.3 | $ 1.3

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