Indebtedness - Fair Value and Carrying Value of Long-Term Debt (Detail) - USD ($) $ in Millions	6 Months Ended	9 Months Ended
Jun. 30, 2020	Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Carrying Amount		$ 6,363	$ 5,581
Estimated Fair Value		7,163	6,078
4.50% 2012 Senior Notes, due 2022
Debt Instrument [Line Items]
Carrying Amount		514	507
Estimated Fair Value		$ 535	$ 531
Notes payable, interest rate		4.50%	4.50%
4.875% 2013 Senior Notes, due 2024
Debt Instrument [Line Items]
Carrying Amount		$ 498	$ 497
Estimated Fair Value		$ 565	$ 551
Notes payable, interest rate		4.875%	4.875%
5.25% 2014 Senior Notes (30-Year), due 2044
Debt Instrument [Line Items]
Carrying Amount		$ 599	$ 599
Estimated Fair Value		$ 822	$ 757
Notes payable, interest rate		5.25%	5.25%
Debt instrument, term	30 years	30 years
1.75% 2015 Senior Notes, due 2027
Debt Instrument [Line Items]
Carrying Amount			$ 558
Estimated Fair Value		$ 643	$ 604
Notes payable, interest rate		1.75%	1.75%
2.75% 2017 Senior Notes, due 2021
Debt Instrument [Line Items]
Carrying Amount		$ 584	$ 508
Estimated Fair Value			$ 507
Notes payable, interest rate		2.75%	2.75%
2.625% 2017 Senior Notes, due 2023
Debt Instrument [Line Items]
Carrying Amount		$ 510	$ 504
Estimated Fair Value		$ 523	$ 507
Notes payable, interest rate		2.625%	2.625%
3.25% 2017 Senior Notes, due 2028
Debt Instrument [Line Items]
Carrying Amount		$ 527	$ 493
Estimated Fair Value		$ 566	$ 523
Notes payable, interest rate		3.25%	3.25%
3.25% 2018 Senior Notes, due 2021
Debt Instrument [Line Items]
Carrying Amount			$ 299
Estimated Fair Value			$ 306
Notes payable, interest rate		3.25%	3.25%
4.25% 2018 Senior Notes, due 2029
Debt Instrument [Line Items]
Carrying Amount		$ 395	$ 394
Estimated Fair Value		$ 479	$ 453
Notes payable, interest rate		4.25%	4.25%
4.875% 2018 Senior Notes, due 2048
Debt Instrument [Line Items]
Carrying Amount		$ 389	$ 389
Estimated Fair Value		$ 540	$ 492
Notes payable, interest rate		4.875%	4.875%
0.950% Senior Notes Due 2030
Debt Instrument [Line Items]
Carrying Amount		$ 870	$ 833
Estimated Fair Value		$ 923	$ 847
Notes payable, interest rate		0.95%	0.95%
3.75% 2020 Senior Notes, due 2025
Debt Instrument [Line Items]
Carrying Amount		$ 693
Estimated Fair Value		$ 789
Notes payable, interest rate		3.75%
Debt instrument, term		5 years
3.25% 2020 Senior Notes, due 2050
Debt Instrument [Line Items]
Carrying Amount		$ 293
Estimated Fair Value		$ 320
Notes payable, interest rate		3.25%
Debt instrument, term		30 years
2.55% 2020 Senior Notes, due 2060
Debt Instrument [Line Items]
Carrying Amount		$ 491
Estimated Fair Value		$ 458
Notes payable, interest rate		2.55%
Debt instrument, term		40 years

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=121572278&loc=d3e13433-108611

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

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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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=120520924&loc=SL6031897-161870

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-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=120400017&loc=d3e572229-122910

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-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=120398452&loc=d3e534808-122878

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