Debt and Credit Agreements - Activity Related to Long-Term Debt (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 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	(360)	$ 0
Discount, Premium and Other Activity	2
Long-term Debt as of March 31, 2021, Current Portion	41
Long-term Debt as of March 31, 2021, Long-term Portion	16,306
Long-term Debt as of March 31, 2021, Total	16,347
Current Portion
Movement, Debt Instruments [Roll Forward]
Long-term Debt as of December 31, 2020, Current Portion	401
Long-term Debt Repaid	(360)
Discount, Premium and Other Activity	0
Long-term Debt as of March 31, 2021, Current Portion	41
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
Discount, Premium and Other Activity	2
Long-term Debt as of March 31, 2021, Long-term Portion	$ 16,306

Movement, Debt Instruments [Roll Forward]

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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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
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-Name Accounting Standards Codification
-Topic 230
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-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.8)
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
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-Name Accounting Standards Codification
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Amount of long-term debt and lease obligation, classified as noncurrent.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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- Definition

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

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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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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-Name Accounting Standards Codification
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