Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Includes, but is not limited to, one-time termination benefits, termination of an operating lease or other contract, consolidating or closing facilities, and relocating employees, and termination benefits associated with an ongoing benefit arrangement. Excludes expenses associated with special or contractual termination benefits, a discontinued operation or an asset retirement obligation.

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Name:	us-gaap_BusinessExitCosts1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Restructuring Charges (Summary of Restructuring Charges) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Jul. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Restructuring Cost and Reserve [Line Items]
Total restructuring charges		$ 0	$ 4	$ 12	$ 9
E&P
Restructuring Cost and Reserve [Line Items]
Total restructuring charges			4	12	9
Workforce Reduction
Restructuring Cost and Reserve [Line Items]
Severance (including payroll taxes)		0	1	12	4
Office consolidation	$ 3	0	3	0	5
Total restructuring charges		$ 0	4	12	9
Workforce Reduction \| E&P
Restructuring Cost and Reserve [Line Items]
Total restructuring charges			$ 4	$ 12	$ 9