Restructuring and Separation Costs - Other Restructuring Costs (Details) $ in Millions	9 Months Ended
Sep. 30, 2018 USD ($)
Restructuring Reserve
Accrued as of December 31, 2017	$ 48
Adjustments	9
Charges	8
Cash payments	(32)
Accrued as of September 30, 2018	33
Separation Costs - Former Executives
Restructuring Reserve
Accrued as of December 31, 2017	2
Adjustments	0
Charges	0
Cash payments	(2)
Accrued as of September 30, 2018	0
One-Time Termination Benefits
Restructuring Reserve
Accrued as of December 31, 2017	11
Adjustments	(1)
Charges	6
Cash payments	(15)
Accrued as of September 30, 2018	1
Other Restructuring Costs
Restructuring Reserve
Accrued as of December 31, 2017	35
Adjustments	10
Charges	2
Cash payments	(15)
Accrued as of September 30, 2018	32
IT Restructuring
Restructuring Reserve
Accrued as of December 31, 2017	0
Charges	3
Cash payments	0
Accrued as of September 30, 2018	3
IT Restructuring \| One-Time Termination Benefits
Restructuring Reserve
Accrued as of December 31, 2017	0
Charges	2
Cash payments	0
Accrued as of September 30, 2018	2
IT Restructuring \| Other Restructuring Costs
Restructuring Reserve
Accrued as of December 31, 2017	0
Charges	1
Cash payments	0
Accrued as of September 30, 2018	$ 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.

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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.

+ References

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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.

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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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