Blount Station (Details) (USD $)	12 Months Ended
	Dec. 31, 2011 MW	Dec. 31, 2010
Blount Capacity Megawatts [Abstract]
Blount capacity current - MW	190
Blount capacity future - MW	100
Blount capacity reduction - MW	90
Restructuring and related costs [Abstract]
Benefits expected to be paid	$ 300,000
Restructuring accrual activity [Roll forward]
Restructuring reserve, beginning balance	259,000
Additional expense, net	58,000
Cash payments during the period	24,000
Restructuring reserve, ending balance	293,000	259,000
Accelerated Depreciation Recovered [Abstract]
Accelerated depreciation recovered	$ 3,400,000	$ 3,400,000