Financial Instruments Cash Flow Hedges Included in AOCI (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
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Remaining Maturity					2 years
After-tax net loss to be reclassified from AOCL into earnings over the next twelve months					$ 9
Successor [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Additions and revaluations of derivatives designated as cash flow hedges	$ 0		$ (5)		(4)
Predecessor [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Additions and revaluations of derivatives designated as cash flow hedges		$ 1		$ 5
Cash Flow Hedging [Member] | Successor [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Beginning Balance	0		(7)		(2)
Additions and revaluations of derivatives designated as cash flow hedges	0		(3)		(3)
Clearance of hedge results to earnings	0				(5)
Ending Balance	0	0	$ (10)	0	$ (10)
Cash Flow Hedging [Member] | Predecessor [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Beginning Balance	$ (3)	(4)		7
Additions and revaluations of derivatives designated as cash flow hedges		1		3
Clearance of hedge results to earnings				(13)
Ending Balance		$ (3)		$ (3)