Derivative Instruments (Details) - Successor - Not Designated as Hedging Instrument - Natural gas swap contracts $ in Thousands, BTU in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2017 USD ($) BTU	Dec. 31, 2016 USD ($) BTU
Commodity Contract, Maturity Q4 2017
Derivative [Line Items]
Derivative energy measure (in BTUs) \| BTU	1,980	7,920
Commodity Contract, Maturity Q4 2018
Derivative [Line Items]
Derivative energy measure (in BTUs) \| BTU	2,400
Commodity Contract
Derivative [Line Items]
Natural gas swap contracts, asset	$ 300
Natural gas swap contracts, current asset	250
Natural gas swap contracts, noncurrent asset	$ 50
Natural gas swap contracts, current liability		$ 3,800

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