(Schedules of Net Periodic Benefit Cost) (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, 2016	Aug. 31, 2017	Sep. 30, 2016
Pension Plan | Successor
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 12
Interest cost	62
Expected return on plan assets	(102)
Amortization of loss	0
Amortization of prior service benefit	0
Curtailment (gain) loss	0
Settlement loss	0
Net periodic benefit (credit) cost	(28)
Pension Plan | Successor | Discontinued Operations [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (credit) cost	0
Pension Plan | Successor | Continuing Operations [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (credit) cost	(28)
Pension Plan | Predecessor
Defined Benefit Plan Disclosure [Line Items]
Service cost		$ 25	$ 44	$ 92	$ 133
Interest cost		132	189	524	612
Expected return on plan assets		(207)	(327)	(824)	(996)
Amortization of loss		127	229	506	605
Amortization of prior service benefit		(1)	(2)	(3)	(5)
Curtailment (gain) loss		0	(1)	0	65
Settlement loss		0	22	0	60
Net periodic benefit (credit) cost		76	154	295	474
Pension Plan | Predecessor | Discontinued Operations [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (credit) cost		1	1	3	0
Pension Plan | Predecessor | Continuing Operations [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (credit) cost		75	153	292	474
Other Post Employment Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Curtailment (gain) loss					(33)
Other Post Employment Benefit Plans | Successor
Defined Benefit Plan Disclosure [Line Items]
Service cost	1
Interest cost	6
Amortization of loss	0
Amortization of prior service benefit	0
Curtailment (gain) loss	0
Other Post Employment Benefit Plans | Successor | Continuing Operations [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (credit) cost	$ 7
Other Post Employment Benefit Plans | Predecessor
Defined Benefit Plan Disclosure [Line Items]
Service cost		2	2	6	9
Interest cost		15	20	60	64
Amortization of loss		15	21	61	56
Amortization of prior service benefit		(11)	(36)	(46)	(111)
Curtailment (gain) loss		0	0	0	(33)
Other Post Employment Benefit Plans | Predecessor | Continuing Operations [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (credit) cost		$ 21	$ 7	$ 81	$ (15)