Indebtedness - Fair Value and Carrying Value of Long-Term Debt (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Carrying Amount	$ 5,581	$ 5,676
2010 Senior Notes due 2020
Debt Instrument [Line Items]
Notes payable, interest rate	5.50%	5.50%
Carrying Amount	$ 0	$ 494
4.50% 2012 Senior Notes, due 2022
Debt Instrument [Line Items]
Notes payable, interest rate	4.50%	4.50%
Carrying Amount	$ 507	$ 499
4.875% 2013 Senior Notes, due 2024
Debt Instrument [Line Items]
Notes payable, interest rate	4.875%	4.875%
Carrying Amount	$ 497	$ 497
2.75% 2014 Senior Notes (5-Year), due 2019
Debt Instrument [Line Items]
Notes payable, interest rate	2.75%	2.75%
Term of notes	5 years	5 years
Carrying Amount	$ 0	$ 450
5.25% 2014 Senior Notes (30-Year), due 2044
Debt Instrument [Line Items]
Notes payable, interest rate	5.25%	5.25%
Term of notes	30 years	30 years
Carrying Amount	$ 599	$ 598
1.75% 2015 Senior Notes, due 2027
Debt Instrument [Line Items]
Notes payable, interest rate	1.75%	1.75%
Carrying Amount	$ 558	$ 569
2.75% 2017 Senior Notes, due 2021
Debt Instrument [Line Items]
Notes payable, interest rate	2.75%	2.75%
Carrying Amount	$ 508	$ 501
2.625% 2017 Senior Notes, due 2023
Debt Instrument [Line Items]
Notes payable, interest rate	2.625%	2.625%
Carrying Amount	$ 504	$ 496
3.25% 2017 Senior Notes, due 2028
Debt Instrument [Line Items]
Notes payable, interest rate	3.25%	3.25%
Carrying Amount	$ 493	$ 491
3.25% 2018 Senior Notes, due 2021
Debt Instrument [Line Items]
Notes payable, interest rate	3.25%	3.25%
Carrying Amount	$ 299	$ 298
4.25% 2018 Senior Notes, due 2029
Debt Instrument [Line Items]
Notes payable, interest rate	4.25%	4.25%
Carrying Amount	$ 394	$ 394
4.875% 2018 Senior Notes, due 2048
Debt Instrument [Line Items]
Notes payable, interest rate	4.875%	4.875%
Carrying Amount	$ 389	$ 389
0.950% Senior Notes Due 2030
Debt Instrument [Line Items]
Notes payable, interest rate	0.95%
Carrying Amount	$ 833	0
Level 2
Debt Instrument [Line Items]
Estimated Fair Value	6,078	5,783
Level 2 \| 2010 Senior Notes due 2020
Debt Instrument [Line Items]
Estimated Fair Value	0	518
Level 2 \| 4.50% 2012 Senior Notes, due 2022
Debt Instrument [Line Items]
Estimated Fair Value	531	514
Level 2 \| 4.875% 2013 Senior Notes, due 2024
Debt Instrument [Line Items]
Estimated Fair Value	551	522
Level 2 \| 2.75% 2014 Senior Notes (5-Year), due 2019
Debt Instrument [Line Items]
Estimated Fair Value	0	450
Level 2 \| 5.25% 2014 Senior Notes (30-Year), due 2044
Debt Instrument [Line Items]
Estimated Fair Value	757	638
Level 2 \| 1.75% 2015 Senior Notes, due 2027
Debt Instrument [Line Items]
Estimated Fair Value	604	585
Level 2 \| 2.75% 2017 Senior Notes, due 2021
Debt Instrument [Line Items]
Estimated Fair Value	507	490
Level 2 \| 2.625% 2017 Senior Notes, due 2023
Debt Instrument [Line Items]
Estimated Fair Value	507	477
Level 2 \| 3.25% 2017 Senior Notes, due 2028
Debt Instrument [Line Items]
Estimated Fair Value	523	473
Level 2 \| 3.25% 2018 Senior Notes, due 2021
Debt Instrument [Line Items]
Estimated Fair Value	306	299
Level 2 \| 4.25% 2018 Senior Notes, due 2029
Debt Instrument [Line Items]
Estimated Fair Value	453	407
Level 2 \| 4.875% 2018 Senior Notes, due 2048
Debt Instrument [Line Items]
Estimated Fair Value	492	410
Level 2 \| 0.950% Senior Notes Due 2030
Debt Instrument [Line Items]
Estimated Fair Value	$ 847	$ 0

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13433-108611

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Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-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=119400593&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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