Fixed-asset Impairment (Narrative) (Details)	3 Months Ended			9 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Mar. 31, 2014 USD ($) MW	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)
Public Utility, Property, Plant and Equipment [Line Items]
Fixed asset impairment	$ 0	$ 0		$ 0	$ 11,500,000
East Bend Station [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Production plant capacity | MW			186
Fair value			$ 2,700,000
Fixed asset impairment			$ 11,500,000	$ 0	$ 11,500,000