New Accounting Pronouncements New Accounting Pronouncements - Topic 606 (Details) - USD ($) $ in Millions	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Other Current Assets	$ 335	$ 342	$ 332
Other Liabilities, Current	618	692	690
Retained Deficit	$ (6,105)	(5,755)	(5,763)
Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Other Current Assets			332
Other Liabilities, Current			690
Retained Deficit			$ (5,763)
Adjustments Due to Topic 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Other Current Assets		10
Other Liabilities, Current		2
Retained Deficit		$ 8