Retirement and Employee Benefit Plans (Fair Value Measurement of Pension Plan Assets) (Details) - Pension Benefits - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 106	$ 96	$ 91
Excluding Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	101	67
Excluding Net Asset Value | Equity securities, U.S. large cap value equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10	6
Excluding Net Asset Value | Equity securities, U.S. large cap core equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	24
Excluding Net Asset Value | Equity securities, U.S. small cap equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13	2
Excluding Net Asset Value | Non-U.S. equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	18	32
Excluding Net Asset Value | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	34	22
Excluding Net Asset Value | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2	2
Excluding Net Asset Value | Equity securities, U.S. large cap growth equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		3
Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	101	67
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	10	6
Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity securities, U.S. large cap core equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	24
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	13	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	18	32
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	34	22
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	2
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
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 value 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 core equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	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) | 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 Observable Inputs (Level 2) | Equity securities, U.S. large cap growth equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		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 value 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 core equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	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) | 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
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
Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5	29
Net Asset Value | Equity securities, U.S. large cap core equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		18
Net Asset Value | Equity securities, U.S. small cap equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2
Net Asset Value | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		8
Net Asset Value | Equity securities, U.S. large cap growth equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 3	$ 3