Fair Value Measurements (Details) - Fair Value, Recurring [Member] - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Natural Gas Derivative [Member]
Debt Instrument [Line Items]
Derivative Asset	$ 11.7	$ 7.5
Derivative Liability	0.2	1.0
Natural Gas Basis Derivative [Member]
Debt Instrument [Line Items]
Derivative Asset	3.4	0.4
Derivative Liability	0.9	5.3
Oil Derivative [Member]
Debt Instrument [Line Items]
Derivative Asset	1.6	6.9
Derivative Liability	7.0
Natural Gas Liquid Derivative [Member]
Debt Instrument [Line Items]
Derivative Asset		4.7
Derivative Liability		0.2
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	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] | Oil Derivative [Member]
Debt Instrument [Line Items]
Derivative Asset	0.0	0.0
Derivative Liability	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 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	11.7	7.5
Derivative Liability	0.2	1.0
Fair Value, Inputs, Level 2 [Member] | Natural Gas Basis Derivative [Member]
Debt Instrument [Line Items]
Derivative Asset	3.4	0.4
Derivative Liability	0.9	5.3
Fair Value, Inputs, Level 2 [Member] | Oil Derivative [Member]
Debt Instrument [Line Items]
Derivative Asset	1.6	6.9
Derivative Liability	7.0
Fair Value, Inputs, Level 2 [Member] | Natural Gas Liquid Derivative [Member]
Debt Instrument [Line Items]
Derivative Asset		4.7
Derivative Liability		0.2
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	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] | Oil Derivative [Member]
Debt Instrument [Line Items]
Derivative Asset	0.0	0.0
Derivative Liability	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 Basis Derivative [Member]
Debt Instrument [Line Items]
Derivative Liability	$ 0.0