Contingencies and Off-Balance Sheet Commitments (Details) (USD $)	Mar. 31, 2012	Dec. 31, 2011
Environmental indemnification obligations
Aggregate amounts accrued for environmental liabilities	$ 1,500,000	$ 1,500,000
Legal Proceedings
Liability recorded for public liability and property damage matters	$ 281,047,000	$ 281,534,000

Total costs accrued as of the balance sheet date for environmental loss contingencies.

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