Fair Value Measurements (Details) - Fair Value, Measurements, Recurring [Member] - Successor [Member] - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Natural Gas Derivative [Member]
Debt Instrument [Line Items]
Derivative Asset	$ 7.2
Derivative Liability	1.3	$ 13.7
Natural Gas Basis Derivative [Member]
Debt Instrument [Line Items]
Derivative Asset	0.3	0.4
Derivative Liability	0.3	0.1
Natural Gas Liquid Derivative [Member]
Debt Instrument [Line Items]
Derivative Asset	0.1
Derivative Liability	0.9
Oil Derivative [Member]
Debt Instrument [Line Items]
Derivative Liability	5.2	3.0
Oil Basis Derivative [Member]
Debt Instrument [Line Items]
Derivative Liability	0.1
Fair Value, Inputs, Level 1 [Member] | Natural Gas Derivative [Member]
Debt Instrument [Line Items]
Derivative Asset	0.0
Derivative Liability	0.0	0.0
Fair Value, Inputs, Level 1 [Member] | Natural Gas Basis Derivative [Member]
Debt Instrument [Line Items]
Derivative Asset	0.0	0.0
Derivative Liability	0.0	0.0
Fair Value, Inputs, Level 1 [Member] | Natural Gas Liquid Derivative [Member]
Debt Instrument [Line Items]
Derivative Asset	0.0
Derivative Liability	0.0
Fair Value, Inputs, Level 1 [Member] | Oil Derivative [Member]
Debt Instrument [Line Items]
Derivative Liability	0.0	0.0
Fair Value, Inputs, Level 1 [Member] | Oil Basis Derivative [Member]
Debt Instrument [Line Items]
Derivative Liability	0.0
Fair Value, Inputs, Level 2 [Member] | Natural Gas Derivative [Member]
Debt Instrument [Line Items]
Derivative Asset	7.2
Derivative Liability	1.3	13.7
Fair Value, Inputs, Level 2 [Member] | Natural Gas Basis Derivative [Member]
Debt Instrument [Line Items]
Derivative Asset	0.3	0.4
Derivative Liability	0.3	0.1
Fair Value, Inputs, Level 2 [Member] | Natural Gas Liquid Derivative [Member]
Debt Instrument [Line Items]
Derivative Asset	0.1
Derivative Liability	0.9
Fair Value, Inputs, Level 2 [Member] | Oil Derivative [Member]
Debt Instrument [Line Items]
Derivative Liability	5.2	3.0
Fair Value, Inputs, Level 2 [Member] | Oil Basis Derivative [Member]
Debt Instrument [Line Items]
Derivative Liability	0.1
Fair Value, Inputs, Level 3 [Member] | Natural Gas Derivative [Member]
Debt Instrument [Line Items]
Derivative Asset	0.0
Derivative Liability	0.0	0.0
Fair Value, Inputs, Level 3 [Member] | Natural Gas Basis Derivative [Member]
Debt Instrument [Line Items]
Derivative Asset	0.0	0.0
Derivative Liability	0.0	0.0
Fair Value, Inputs, Level 3 [Member] | Natural Gas Liquid Derivative [Member]
Debt Instrument [Line Items]
Derivative Asset	0.0
Derivative Liability	0.0
Fair Value, Inputs, Level 3 [Member] | Oil Derivative [Member]
Debt Instrument [Line Items]
Derivative Liability	0.0	$ 0.0
Fair Value, Inputs, Level 3 [Member] | Oil Basis Derivative [Member]
Debt Instrument [Line Items]
Derivative Liability	$ 0.0