Fair Value Measurements (Details 2) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Price Risk Cash Flow Hedge Asset, at Fair Value	$ 0.4
Natural Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Price Risk Cash Flow Hedge Asset, at Fair Value	0.1
Natural Gas [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Price Risk Cash Flow Hedge Asset, at Fair Value	0
Natural Gas [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Price Risk Cash Flow Hedge Asset, at Fair Value	0.1
Natural Gas [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Price Risk Cash Flow Hedge Asset, at Fair Value	0
Oil [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Price Risk Cash Flow Hedge Asset, at Fair Value	0.3
Oil [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Price Risk Cash Flow Hedge Asset, at Fair Value	0
Oil [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Price Risk Cash Flow Hedge Asset, at Fair Value	0.3
Oil [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Price Risk Cash Flow Hedge Asset, at Fair Value	$ 0