Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	$ 86	$ 276	$ (269)	$ 662
Other AOCI activity	(73)	(338)	282	(724)
Balance at end of period	13	(62)	13	(62)
Foreign Currency Translation Adjustments
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	425	617	79	1,016
Other AOCI activity	(78)	(345)	268	(744)
Balance at end of period	347	272	347	272
Pension and Post-retirement Benefit Plan Obligations
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	(337)	(338)	(346)	(351)
Other AOCI activity	5	6	14	19
Balance at end of period	(332)	(332)	(332)	(332)
Gas Purchase Contract Hedges
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	0	0	(3)	(3)
Other AOCI activity	0	0	3	3
Balance at end of period	0	0	0	0
Other
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	(2)	(3)	1	0
Other AOCI activity	0	1	(3)	(2)
Balance at end of period	$ (2)	$ (2)	$ (2)	$ (2)