Related Party Transaction (Related Party Transaction - Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Related Party Transaction [Line Items]
Interest Expense, Debt	$ 67	$ 68	$ 73
Operating Expenses	1,738	1,722	1,764
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Interest Expense, Debt	65	64	70
Operating Expenses	$ 820	$ 1,000	$ 985