Supplementary Information Foreign Currency Exchange Gain (Loss) (Details) - USD ($) $ in Millions	4 Months Ended	8 Months Ended	12 Months Ended
	Dec. 31, 2017	Aug. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Successor [Member]
Foreign Currency Exchange Gain (Loss) [Line Items]
Foreign Currency Transaction Gain (Loss), before Tax	$ 8
Foreign Currency Transaction Gain (Loss) Tax	(36)
Foreign Currency Transaction Gain (Loss) After Tax	(28)
Predecessor [Member]
Foreign Currency Exchange Gain (Loss) [Line Items]
Foreign Currency Transaction Gain (Loss), before Tax		$ (394)	$ (106)	$ 30
Foreign Currency Transaction Gain (Loss) Tax		372	(16)	(218)
Foreign Currency Transaction Gain (Loss) After Tax		(22)	(122)	(188)
Subsidiary Monetary Position | Successor [Member]
Foreign Currency Exchange Gain (Loss) [Line Items]
Foreign Currency Transaction Gain (Loss), before Tax	(83)
Foreign Currency Transaction Gain (Loss) Tax	(3)
Foreign Currency Transaction Gain (Loss) After Tax	(86)
Subsidiary Monetary Position | Predecessor [Member]
Foreign Currency Exchange Gain (Loss) [Line Items]
Foreign Currency Transaction Gain (Loss), before Tax		37	198	(404)
Foreign Currency Transaction Gain (Loss) Tax		217	(126)	(61)
Foreign Currency Transaction Gain (Loss) After Tax		254	72	(465)
Hedging Program [Member] | Successor [Member]
Foreign Currency Exchange Gain (Loss) [Line Items]
Foreign Currency Transaction Gain (Loss), before Tax	91
Foreign Currency Transaction Gain (Loss) Tax	(33)
Foreign Currency Transaction Gain (Loss) After Tax	$ 58
Hedging Program [Member] | Predecessor [Member]
Foreign Currency Exchange Gain (Loss) [Line Items]
Foreign Currency Transaction Gain (Loss), before Tax		(431)	(304)	434
Foreign Currency Transaction Gain (Loss) Tax		155	110	(157)
Foreign Currency Transaction Gain (Loss) After Tax		$ (276)	$ (194)	$ 277