Borrowings - Carrying Value and Fair Value of Long-Term Borrowings (Detail) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Maturity Amount	$ 5,061
Unamortized Discount and Debt Issuance Costs	(25)
Carrying Value	5,036	$ 5,014
Fair Value	5,134
5.00% Notes due 2019 [Member]
Debt Instrument [Line Items]
Maturity Amount	1,000
Carrying Value	1,000
Fair Value	1,039
4.25% Notes due 2021 [Member]
Debt Instrument [Line Items]
Maturity Amount	750
Unamortized Discount and Debt Issuance Costs	(2)
Carrying Value	748
Fair Value	774
3.375% Notes due 2022 [Member]
Debt Instrument [Line Items]
Maturity Amount	750
Unamortized Discount and Debt Issuance Costs	(4)
Carrying Value	746
Fair Value	759
3.50% Notes due 2024 [Member]
Debt Instrument [Line Items]
Maturity Amount	1,000
Unamortized Discount and Debt Issuance Costs	(6)
Carrying Value	994
Fair Value	1,006
1.25% Notes due 2025 [Member]
Debt Instrument [Line Items]
Maturity Amount	861
Unamortized Discount and Debt Issuance Costs	(6)
Carrying Value	855
Fair Value	877
3.20% Notes due 2027 [Member]
Debt Instrument [Line Items]
Maturity Amount	700
Unamortized Discount and Debt Issuance Costs	(7)
Carrying Value	693
Fair Value	$ 679

Face (par) amount of debt instrument at time of issuance.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

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+ References

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Amount of unamortized debt discount (premium) and debt issuance costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28555-108399

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- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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