Significant Accounting Policies (Intangible Assets) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross	$ 179	$ 189
Less: Accumulated Amortization	45	34
Intangible Assets, Net	134	155
Less current intangible assets	12	20
Finite-Lived Intangible Assets, Net	122	135
Emission Allowances [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross	2	6
Renewable Energy Credits [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross	51	44
Contract Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross	$ 126	$ 139