Fair Value Measurements (Details 2) (Oil Floors [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Price Risk Cash Flow Hedge Asset, at Fair Value	$ 0.1
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
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
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