Investments in Unconsolidated Affiliates - Narrative (Details) (Medusa Spar LLC Investment [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2003
Medusa Spar LLC Investment [Member]
Schedule of Equity Method Investments [Line Items]
Percentage of equity method investment	50.00%
Equity Method Investment, Aggregate Cost		$ 43.7
Equity Method Investment, Significant Property, Plant and Equipment Owned by Equity Method Investee	75.00%
Equity Method Investment, Significant Property, Plant and Equipment Owned by Equity Method Investee, Percentage Financed by Debt	50.00%
Equity Method Investment, Significant Property, Plant and Equipment Owned by Equity Method Investee, Percentage Financed by Equity	50.00%
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	$ 47

Equity Method Investment, Significant Property, Plant and Equipment Owned by Equity Method Investee

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Equity Method Investment, Significant Property, Plant and Equipment Owned by Equity Method Investee, Percentage Financed by Debt

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- Definition

Equity Method Investment, Significant Property, Plant and Equipment Owned by Equity Method Investee, Percentage Financed by Equity

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No definition available.

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- Definition

This element represents the aggregate cost of investments accounted for under the equity method of accounting.

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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- Definition

The reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE).

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