Contingencies and Off-Balance Sheet Commitments (Details) (USD $)	Mar. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Environmental indemnification obligations
Aggregate amounts accrued for environmental liabilities	$ 2,600,000	$ 2,600,000	$ 1,500,000
Legal Proceedings
Liability recorded for public liability and property damage matters	321,003,000	332,232,000	281,534,000
Pending Litigation \| Sobel Case
Legal Proceedings
Estimate of possible loss	$ 40,000,000

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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