Fair Value Measurements (Details 2) - Fair Value, Measurements, Recurring [Member] $ in Millions	Dec. 31, 2014 USD ($)
Natural Gas Derivative Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value of Derivative Asset	$ 2.4
Fair Value of Derivative Liability	0.1
Natural Gas Derivative Contract [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value of Derivative Asset	0.0
Fair Value of Derivative Liability	0.0
Natural Gas Derivative Contract [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value of Derivative Asset	2.4
Fair Value of Derivative Liability	0.1
Natural Gas Derivative Contract [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value of Derivative Asset	0.0
Fair Value of Derivative Liability	0.0
Natural Gas Basis Derivative Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value of Derivative Asset	0.1
Natural Gas Basis Derivative Contract [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value of Derivative Asset	0.0
Natural Gas Basis Derivative Contract [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value of Derivative Asset	0.1
Natural Gas Basis Derivative Contract [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value of Derivative Asset	$ 0.0