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Commitments - Narrative (Details) |  |  | 12 Months Ended
--- | --- | --- | ---
Jan. 01, 2017 | Mar. 11, 1997 USD ($) well | Dec. 31, 2018 USD ($) MMBtu_per_day well | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($)
Commitments [Line Items] |  |  |  |  |
Plugging and abandonment escrow account on the WCBB properties (Note 15) |  |  | $ 3,100,000 |  |
Maximum annual contributions per employee (401K Plan) |  |  | 100.00% |  |
Cost recognized on defined contribution plan |  |  | $ 2,600,000 | $ 3,000,000 | $ 1,700,000
Purchase commitment daily volume | MMBtu_per_day |  |  | 2,300,000 |  |
Chief Executive Officer |  |  |  |  |
Commitments [Line Items] |  |  |  |  |
Payment of separation costs |  |  | $ 400,000 |  |
Management |  |  |  |  |
Commitments [Line Items] |  |  |  |  |
Employment agreement term | 1 year |  |  |  |
Employment agreement, subsequent extension | 1 year |  |  |  |
Employment agreement, notice period allowed for termination | 30 days |  |  |  |
Minimum |  |  |  |  |
Commitments [Line Items] |  |  |  |  |
Minimum matching employer contribution for 401K |  |  | 3.00% |  |
Operating lease term (exceeding one year) |  |  | 1 year |  |
Supply agreement non-utilization fees | Muskie Proppant LLC |  |  |  |  |
Commitments [Line Items] |  |  |  |  |
Non-utilization fees incurred |  |  | $ 2,200,000 | $ 0 |
WCBB |  |  |  |  |
Commitments [Line Items] |  |  |  |  |
Remaining percent interest in properties |  | 50.00% |  |  |
Monthly payments to abandonment trust obligation |  | $ 18,000 |  |  |
Plugging commitment (wells) | well |  | 20 |  |  |
Period of well plugging commitment |  | 20 years |  |  |
Number of wells plugged to date | well |  |  | 555 |  |

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