Equity Investments (Schedule of Financial Information Related to Unconsolidated Entities Included in Consolidated Statement of Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Equity Investments [Abstract]
Revenues	$ 65	$ 368	$ 657	$ 1,115
Operating costs and expenses	63	329	537	962
Income from continuing operations before taxes	$ 2	$ 39	$ 120	$ 153