Other Income (Expense), Net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Income and Expenses [Abstract]
Net Foreign Currency Transaction Gains (Losses)	$ 8	$ (41)	$ (17)
Interest income	8		3
Equity income from investments in Trinidad	3	4	9
Adjustment to Deferred Compensation Expense	$ (6)	$ (11)	$ 6