Contingent Liabilities and Commitments (Details Textual) (USD $)	3 Months Ended			3 Months Ended			3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013 Capital Additions [Member]	Mar. 31, 2013 Potentially Responsible Party At Various Superfund And State Waste Disposal Sites [Member]	Mar. 31, 2013 Environmental Restoration Costs [Member]	Dec. 31, 2012 Environmental Restoration Costs [Member]	Mar. 31, 2013 Minimum [Member]	Mar. 31, 2013 Maximum [Member]
Environmental Matters [Abstract]
Aggregate, Loss Exposure Not Accrued, Low Estimate	$ 5,000,000
Aggregate, Loss Exposure Not Accrued, High Estimate	7,000,000			500,000
Expected Duration Of Environmental Assessment And Remediation Spending							3 years	5 years
Accrual for Environmental Loss Contingencies, Total	3,100,000	3,300,000
Accrued Environmental Loss Contingencies, Current	1,100,000	1,100,000
Accrued Environmental Loss Contingencies, Noncurrent	2,000,000	2,200,000
Estimated Capital Costs For Compliance With Hazardous Air Pollutant Regulations							10,000,000	12,000,000
Regulatory Assets					0	0
Commitments For Construction [Abstract]
Purchase Commitment, Remaining Minimum Amount Committed			$ 316,000,000