Significant Accounting Policies (Intangible Assets) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$ 52	$ 53
Less Current Intangible Assets	13	12
Finite-Lived Intangible Assets, Net	39	41
Emission Allowances [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	2	2
Renewable Energy Credits [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$ 50	$ 51