Commitments, Contingencies and Uncertainties (Purchase Allowance For Compliance) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Site Contingency [Line Items]
Purchase allowance for reduction of NOx emissions	$ 37	$ 90	$ 370