Long-Term Investments (Equity Method Investments) (Details)	12 Months Ended
	Dec. 31, 2012
Keystone [Member]
Long-Term Investments [Line Items]
Location of the affiliated companies, equity method investments	PA
Owned percentage	23.00%
Conemaugh [Member]
Long-Term Investments [Line Items]
Location of the affiliated companies, equity method investments	PA
Owned percentage	23.00%
Kalaeloa [Member]
Long-Term Investments [Line Items]
Location of the affiliated companies, equity method investments	HI
Owned percentage	50.00%
Gwf Energy Llc [Member]
Long-Term Investments [Line Items]
Location of the affiliated companies, equity method investments	CA
Owned percentage	50.00%
Hanford L. P. (Hanford) [Member]
Long-Term Investments [Line Items]
Location of the affiliated companies, equity method investments	CA
Owned percentage	50.00%