Organization and Basis of Presentation (Summarized Income Statement Data) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Operating Revenues	$ 1,210	$ 883	$ 756
Operating Expenses	853	622	561
Net Income	$ 313	$ 365	$ 254