Expenses - Restructuring Reserve (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Restructuring Reserve [Roll Forward]
Beginning balance	$ 198	$ 341
Accruals for Beacon		(4)
Accruals for Repositioning Charges		0
Payments and Other Adjustments	(34)	(78)
Ending balance	164	259
Employee Related Costs
Restructuring Reserve [Roll Forward]
Beginning balance	190	303
Accruals for Beacon		(4)
Accruals for Repositioning Charges		0
Payments and Other Adjustments	(33)	(53)
Ending balance	157	246
Real Estate Actions
Restructuring Reserve [Roll Forward]
Beginning balance	7	37
Accruals for Beacon		0
Accruals for Repositioning Charges		0
Payments and Other Adjustments	(1)	(25)
Ending balance	6	12
Asset and Other Write-offs
Restructuring Reserve [Roll Forward]
Beginning balance	1	1
Accruals for Beacon		0
Accruals for Repositioning Charges		0
Payments and Other Adjustments	0	0
Ending balance	$ 1	$ 1

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.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
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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.

+ References

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- Definition

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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Amount of expense (reversal of expense) which increases (decreases) the restructuring reserve from an adjustment to a previously accrued restructuring liability.

+ References

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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No definition available.

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