Fair Value of FInancial Instruments Fair Value Options Quantitative Disclosure (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Option, Quantitative Disclosures [Line Items]
Commodity Contract Asset, Natural gas	$ 4,000,000	$ 5,000,000
Commodity Contract Liabilities, Electricity	127,000,000	82,000,000
Commodity Contract Liabilities, Natural gas	63,000,000	118,000,000
Assets [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Electricity physical forward purchase	0
Natural gas financial swaps	0	2,000,000
Fnancial swaps - electricity	1,000,000	0
Total commodity contracts	1,000,000	2,000,000
Derivative Financial Instruments, Liabilities [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Electricity physical forward purchase	103,000,000
Natural gas financial swaps	23,000,000	8,000,000
Fnancial swaps - electricity	14,000,000	10,000,000
Total commodity contracts	140,000,000	18,000,000
Fair Value, Inputs, Level 3 [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Commodity Contract Asset, Natural gas	0	2,000,000
Commodity Contract Liabilities, Electricity	117,000,000	10,000,000
Commodity Contract Liabilities, Natural gas	23,000,000	8,000,000
Weighted Average [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Electricity physical forward purchase	40.18
Natural gas financial swaps	3.71	4.28
Fnancial swaps - electricity	33.01	41.14
Maximum [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Electricity physical forward purchase	77.95
Natural gas financial swaps	4.49	5.21
Fnancial swaps - electricity	46.07	51.72
Minimum [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Electricity physical forward purchase	9.63
Natural gas financial swaps	3.16	3.67
Fnancial swaps - electricity	$ 9.63	$ 7.12