Pension Plans and Other Post Employment Benefit Plans Amounts Recognized in Consolidated Balance Sheets (Details) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
Successor [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation		$ 25,100
Noncurrent liabilities		(7,787)
Successor [Member] | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other Assets		47
Net amount recognized		(5,266)
Net (gain) loss		(165)
Prior service benefit		0
Pretax balance in accumulated other comprehensive (income) loss at end of year		(165)
Successor [Member] | Other Post Employment Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other Assets		0
Net amount recognized		(2,810)
Net (gain) loss		68
Prior service benefit		0
Pretax balance in accumulated other comprehensive (income) loss at end of year		68
Predecessor [Member]
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Defined Benefit Plan, Accumulated Benefit Obligation			$ 24,300
Predecessor [Member] | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other Assets			3
Net amount recognized			(8,175)
Net (gain) loss			10,280
Prior service benefit			(17)
Pretax balance in accumulated other comprehensive (income) loss at end of year			10,263
Predecessor [Member] | Other Post Employment Benefits Plan
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Other Assets			0
Net amount recognized			(2,829)
Net (gain) loss			830
Prior service benefit			(281)
Pretax balance in accumulated other comprehensive (income) loss at end of year			549
Accrued and Other Current Liabilities [Member] | Successor [Member] | Pension Plan
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Current liabilities		(86)
Accrued and Other Current Liabilities [Member] | Successor [Member] | Other Post Employment Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current liabilities		(250)
Accrued and Other Current Liabilities [Member] | Predecessor [Member] | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current liabilities			(78)
Accrued and Other Current Liabilities [Member] | Predecessor [Member] | Other Post Employment Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current liabilities			(275)
Liabilities held for sale - current [Member] | Successor [Member] | Pension Plan
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Current liabilities		0
Liabilities held for sale - current [Member] | Successor [Member] | Other Post Employment Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current liabilities		0
Liabilities held for sale - current [Member] | Predecessor [Member] | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current liabilities			(8)
Liabilities held for sale - current [Member] | Predecessor [Member] | Other Post Employment Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current liabilities			0
Pension and other post employment benefits - noncurrent [Member] | Successor [Member] | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Noncurrent liabilities	[1]	(5,227)
Pension and other post employment benefits - noncurrent [Member] | Successor [Member] | Other Post Employment Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Noncurrent liabilities	[1]	(2,560)
Other Noncurrent Obligations [Member] | Successor [Member] | Pension Plan
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Noncurrent liabilities	[1]	0
Other Noncurrent Obligations [Member] | Successor [Member] | Other Post Employment Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Noncurrent liabilities	[1]	$ 0
Other Noncurrent Obligations [Member] | Predecessor [Member] | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Noncurrent liabilities	[1]		(8,092)
Other Noncurrent Obligations [Member] | Predecessor [Member] | Other Post Employment Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Noncurrent liabilities	[1]		$ (2,554)

[1] In the Successor Period, non-current pension and OPEB liabilities are included within pension and other post employment benefits - noncurrent in the Consolidated Balance Sheets. In the Predecessor period, these liabilities are included within other noncurrent obligations.