Commitments, Contingencies And Uncertainties (Costs Incurred To Comply With Federal Environment Statutes) (Details) (USD $)	3 Months Ended			12 Months Ended
	Mar. 31, 2012		Mar. 31, 2011	Mar. 31, 2012		Mar. 31, 2011
Site Contingency [Line Items]
Cost Related to Environmental Litigation at Generation Station	$ 200,000
Clean Air Act
Site Contingency [Line Items]
Environmental Remediation Expense	229,000	[1]	58,000	887,000	[1]	456,000
Clean Water Act
Site Contingency [Line Items]
Environmental Remediation Expense	$ 46,000		$ 56,000	$ 254,000		$ 200,000

[1] (1) Includes an accrual of $0.2 million, in the first quarter of 2012, related to Four Corners generating station discussed below.