Debt and Credit Agreements - Activity Related to Long-Term Debt (Details) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018
Movement, Debt Instruments [Roll Forward]
Long-term debt as of December 31, 2018, Current Portion	$ 18
Long-term debt as of December 31, 2018, Long-term Portion	14,739
Long-term debt as of December 31, 2018, Total	14,757
Long-term debt issued	1,000	$ 2,000
Reclassifications	0
Discount, premium and other activity	10
Long-term debt as of June 30, 2019, Current Portion	245
Long-term debt as of June 30, 2019, Long-term Portion	15,522
Long-term debt as of June 30, 2019, Total	15,767
Current Portion
Movement, Debt Instruments [Roll Forward]
Long-term debt as of December 31, 2018, Current Portion	18
Long-term debt issued	0
Reclassifications	227
Discount, premium and other activity	0
Long-term debt as of June 30, 2019, Current Portion	245
Long-term Portion
Movement, Debt Instruments [Roll Forward]
Long-term debt as of December 31, 2018, Long-term Portion	14,739
Long-term debt issued	1,000
Reclassifications	(227)
Discount, premium and other activity	10
Long-term debt as of June 30, 2019, Long-term Portion	$ 15,522

Movement, Debt Instruments [Roll Forward]

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- Definition

Reclassification of Debt, Long Term Debt to Short Term Debt

+ 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.

+ 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
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28541-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-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=116634182&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
-Topic 944
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-Section S99
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- Definition

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

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

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-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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- Definition

The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
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-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585

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