Financial and Other Derivative Instruments (Cumulative Gross Volume of Derivative Contracts Outstanding) (Details)	Sep. 30, 2014 MMBTU
Natural Gas Commodity Contract [Member]
Derivative [Line Items]
Derivative, Number of Instruments Held	865,462,971
Electricity Commodity Contract [Member]
Derivative [Line Items]
Derivative, Number of Instruments Held	15,291,188
Oil Commodity Contract [Member]
Derivative [Line Items]
Derivative, Number of Instruments Held	10,290,000
Foreign currency exchange contracts [Member]
Derivative [Line Items]
Derivative, Number of Instruments Held	81,310,582