Pension Plans and Other Post Employment Benefit Plans (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	2 Months Ended	3 Months Ended		8 Months Ended	9 Months Ended
	Sep. 30, 2017	Aug. 31, 2017	Dec. 31, 2017	Sep. 30, 2016	Aug. 31, 2017	Sep. 30, 2016	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Other Post Employment Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Weighted Average Discount Rate		3.62%			3.62%		4.03%	3.55%	4.30%
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments						$ 33
Defined Benefit Plan, Re-measurement Impact, Benefit Obligation						265
Predecessor | United States Pension Plan of US Entity [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Contributions by Employer					$ 2,900
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments						(63)
Predecessor | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Weighted Average Discount Rate		3.42%			3.42%		3.80%	3.74%	4.47%
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments		$ 0		$ 1	$ 0	(65)
Defined Benefit Plan Re-measurement Impact, Underfunded Status						2,352
Settlement loss		$ 0		22	0	60
Expected Return on Plan Assets	6.25%	8.00%
Predecessor | Other Post Employment Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments		$ 0		0	$ 0	33
Successor | All Other Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Contributions by Employer	$ 19
Successor | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments	0
Defined Benefit Plan Re-measurement Impact, Underfunded Status	596
Settlement loss	0
Successor | Other Post Employment Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments	0
Defined Benefit Plan, Re-measurement Impact, Benefit Obligation	$ 41
Scenario, Forecast [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Contributions, Remainder of Fiscal Year			$ 50
Pension Restoration Plan [Member] | Predecessor | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Settlement loss				$ 15		$ 51