Debt and Credit Agreements - Activity Related to Long-Term Debt (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020
Movement, Debt Instruments [Roll Forward]
Long-term Debt as of December 31, 2020, Current Portion	$ 401
Long-term Debt as of December 31, 2020, Long-term Portion	16,304
Long-term Debt as of December 31, 2020, Total	16,705
Long-term Debt Repaid	(390)	$ (245)
Reclassifications	0
Finance Lease Obligations and Debt Assumed	68
Discount, Premium and Other Activity	10
Long-term Debt as of September 30, 2021, Current Portion	211
Long-term Debt as of September 30, 2021, Long-term Portion	16,182
Long-term Debt as of September 30, 2021, Total	16,393
Current Portion
Movement, Debt Instruments [Roll Forward]
Long-term Debt as of December 31, 2020, Current Portion	401
Long-term Debt Repaid	(390)
Reclassifications	175
Finance Lease Obligations and Debt Assumed	25
Discount, Premium and Other Activity	0
Long-term Debt as of September 30, 2021, Current Portion	211
Long-term Portion
Movement, Debt Instruments [Roll Forward]
Long-term Debt as of December 31, 2020, Long-term Portion	16,304
Long-term Debt Repaid	0
Reclassifications	(175)
Finance Lease Obligations and Debt Assumed	43
Discount, Premium and Other Activity	10
Long-term Debt as of September 30, 2021, Long-term Portion	$ 16,182

Long-term Debt and Finance Lease Obligations, Increase From Acquisition

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- Definition

Long-term Debt, Increase (Decrease) Due To Reclassifications

+ References

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- Definition

Movement, Debt Instruments [Roll Forward]

+ References

No definition available.

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- Definition

Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

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Amount of short-term and long-term debt and lease obligation.

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Amount of long-term debt and lease obligation, classified as noncurrent.

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Amount of long-term debt and lease obligation, classified as current.

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- Definition

The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

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