Equity Investments (Schedule of Financial Information Related to Unconsolidated Entities Included in Consolidated Statement of Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Equity Investments [Abstract]
Revenues	$ 1,494	$ 1,368	$ 1,246
Operating costs and expenses	1,287	1,184	1,117
Income from continuing operations before taxes	$ 207	$ 184	$ 130