Related Party Transactions (Schedule of related Party Transactions) (Details) - Affiliated Entity - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Related Party Transaction [Line Items]
Interest Income	$ 25	$ 17	$ 20
Interest Expense	33	9	8
Electricity Generation Plant, Non-Nuclear [Member]
Related Party Transaction [Line Items]
Revenue—Non-Regulated	1,099	1,188	1,110
Cost of Sales—Non-Regulated	$ 330	$ 331	$ 276