Commitments, Contingencies And Uncertainties Commitments, Contingencies and Uncertainties (Purchase Allowance For Compliance) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Dec. 31, 2010
Site Contingency [Line Items]
Purchase Allowance for Reduction of NOx Emissions	$ 16	$ 90	$ 370