Pension Plans and Other Post Employment Benefit Plans Components of net periodic benefit cost (credit) (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	Sep. 30, 2018	Aug. 31, 2017	Sep. 30, 2018	Sep. 30, 2017
Successor [Member] | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	$ 12		$ 32		$ 99
Interest Cost	62		186		565
Expected return on plan assets	(102)		(299)		(903)
Amortization of unrecognized (gain) loss	0		0		(1)
Amortization of prior service benefit	0		0		0
Curtailment/settlement (gain) loss	0		2		(2)
Net periodic benefit (credit) cost	(28)		(79)		(242)
Successor [Member] | Other Post Employment Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	1		3		7
Interest Cost	6		20		63
Amortization of unrecognized (gain) loss	0		0		0
Amortization of prior service benefit	0		0		0
Predecessor [Member] | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost		$ 25		$ 92
Interest Cost		132		524
Expected return on plan assets		(207)		(824)
Amortization of unrecognized (gain) loss		127		506
Amortization of prior service benefit		(1)		(3)
Curtailment/settlement (gain) loss		0		0
Net periodic benefit (credit) cost		76		295
Predecessor [Member] | Other Post Employment Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost		2		6
Interest Cost		15		60
Amortization of unrecognized (gain) loss		15		61
Amortization of prior service benefit		(11)		(46)
Discontinued Operations [Member] | Successor [Member] | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit (credit) cost	0		0		0
Discontinued Operations [Member] | Predecessor [Member] | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit (credit) cost		1		3
Continuing Operations [Member] | Successor [Member] | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit (credit) cost	(28)		(79)		(242)
Continuing Operations [Member] | Successor [Member] | Other Post Employment Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit (credit) cost	$ 7		23		70
Continuing Operations [Member] | Predecessor [Member] | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit (credit) cost		75		292
Continuing Operations [Member] | Predecessor [Member] | Other Post Employment Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit (credit) cost		$ 21		$ 81
Principal U.S. Pension Plan [Member] | Successor [Member] | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer Contributions			1,100		1,266
Expected Future Employer Contributions, Current Fiscal Year			$ 1,300		$ 1,300
Principal U.S. Pension Plan [Member] | Predecessor [Member] | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer Contributions						$ 2,900