Retirement and Employee Benefit Plans (Fair Value Measurement of Pension Plan Assets) (Details) - Pension Benefits - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 96	$ 91	$ 101
Cash and cash equivalents | Fayetteville Shale
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	21
Excluding Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	67	72
Excluding Net Asset Value | Equity securities, U.S. large cap growth equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3	5
Excluding Net Asset Value | Equity securities, U.S. large cap value equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6	5
Excluding Net Asset Value | Equity securities, U.S. small cap equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2	2
Excluding Net Asset Value | Non-U.S. equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	32	20
Excluding Net Asset Value | Emerging markets equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		3
Excluding Net Asset Value | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	22	14
Excluding Net Asset Value | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2	23
Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	67	72
Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity securities, U.S. large cap growth equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3	5
Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity securities, U.S. large cap value equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6	5
Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity securities, U.S. small cap equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2	2
Quoted Prices in Active Markets for Identical Assets (Level 1) | Non-U.S. equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	32	20
Quoted Prices in Active Markets for Identical Assets (Level 1) | Emerging markets equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		3
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	22	14
Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2	23
Significant Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Significant Observable Inputs (Level 2) | Equity securities, U.S. large cap growth equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Significant Observable Inputs (Level 2) | Equity securities, U.S. large cap value equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Significant Observable Inputs (Level 2) | Equity securities, U.S. small cap equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Significant Observable Inputs (Level 2) | Non-U.S. equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Significant Observable Inputs (Level 2) | Emerging markets equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Significant Observable Inputs (Level 2) | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Significant Observable Inputs (Level 2) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Significant Unobservable Inputs (Level 3) | Equity securities, U.S. large cap growth equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Significant Unobservable Inputs (Level 3) | Equity securities, U.S. large cap value equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Significant Unobservable Inputs (Level 3) | Equity securities, U.S. small cap equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Significant Unobservable Inputs (Level 3) | Non-U.S. equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Significant Unobservable Inputs (Level 3) | Emerging markets equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Significant Unobservable Inputs (Level 3) | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Significant Unobservable Inputs (Level 3) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	29	19
Net Asset Value | Equity securities, U.S. large cap growth equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3
Net Asset Value | Equity securities, U.S. large cap core equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	18	12
Net Asset Value | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 8	$ 7