Other Expenses (Restructuring Charges) (Details) - Unit Cost Initiative - Other expenses - Severance - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Restructuring Cost and Reserve [Line Items]
Balance, beginning of period	$ 22	$ 17	$ 57	$ 23
Restructuring charges	0	14	0	21
Cash payments	(4)	(11)	(39)	(24)
Balance, end of period	18	20	18	20
Total restructuring charges incurred since inception of initiative	$ 244	$ 157	$ 244	$ 157

Amount of cash payments made as the result of exit or disposal activities. Excludes payments associated with a discontinued operation or an asset retirement obligation.

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Amount of costs incurred to date for the specified restructuring cost.

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Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

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Carrying amount (including both current and noncurrent portions of the accrual) as of the balance sheet date pertaining to a specified type of cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan.

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