Indebtedness - Summary of Total Indebtedness (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Principal Amount	$ 5,603	$ 5,722
Fair Value of Interest Rate Swap	27	2
Unamortized (Discount) Premium	(17)	(18)
Unamortized Debt Issuance Costs	(32)	(30)
Carrying Value	5,581	5,676
Current portion	0	(450)
Total long-term debt	$ 5,581	$ 5,226
5.50% 2010 Senior Notes, due 2020
Debt Instrument [Line Items]
Notes payable, interest rate	5.50%	5.50%
Principal Amount		$ 500
Fair Value of Interest Rate Swap		(4)
Unamortized (Discount) Premium		(1)
Unamortized Debt Issuance Costs		(1)
Carrying Value	$ 0	$ 494
4.50% 2012 Senior Notes, due 2022
Debt Instrument [Line Items]
Notes payable, interest rate	4.50%	4.50%
Principal Amount	$ 500	$ 500
Fair Value of Interest Rate Swap	9	2
Unamortized (Discount) Premium	(1)	(2)
Unamortized Debt Issuance Costs	(1)	(1)
Carrying Value	$ 507	$ 499
4.875% 2013 Senior Notes, due 2024
Debt Instrument [Line Items]
Notes payable, interest rate	4.875%	4.875%
Principal Amount	$ 500	$ 500
Fair Value of Interest Rate Swap	0	0
Unamortized (Discount) Premium	(1)	(1)
Unamortized Debt Issuance Costs	(2)	(2)
Carrying Value	$ 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
Principal Amount		$ 450
Fair Value of Interest Rate Swap		0
Unamortized (Discount) Premium		0
Unamortized Debt Issuance Costs		0
Carrying Value	$ 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
Principal Amount	$ 600	$ 600
Fair Value of Interest Rate Swap	0	0
Unamortized (Discount) Premium	4	3
Unamortized Debt Issuance Costs	(5)	(5)
Carrying Value	$ 599	$ 598
1.75% 2015 Senior Notes, due 2027
Debt Instrument [Line Items]
Notes payable, interest rate	1.75%	1.75%
Principal Amount	$ 561	$ 572
Fair Value of Interest Rate Swap	0	0
Unamortized (Discount) Premium	0	0
Unamortized Debt Issuance Costs	(3)	(3)
Carrying Value	$ 558	$ 569
2.75% 2017 Senior Notes, due 2021
Debt Instrument [Line Items]
Notes payable, interest rate	2.75%	2.75%
Principal Amount	$ 500	$ 500
Fair Value of Interest Rate Swap	11	4
Unamortized (Discount) Premium	(1)	(1)
Unamortized Debt Issuance Costs	(2)	(2)
Carrying Value	$ 508	$ 501
2.625% 2017 Senior Notes, due 2023
Debt Instrument [Line Items]
Notes payable, interest rate	2.625%	2.625%
Principal Amount	$ 500	$ 500
Fair Value of Interest Rate Swap	7	0
Unamortized (Discount) Premium	(1)	(1)
Unamortized Debt Issuance Costs	(2)	(3)
Carrying Value	$ 504	$ 496
3.25% 2017 Senior Notes, due 2028
Debt Instrument [Line Items]
Notes payable, interest rate	3.25%	3.25%
Principal Amount	$ 500	$ 500
Fair Value of Interest Rate Swap	0	0
Unamortized (Discount) Premium	(4)	(5)
Unamortized Debt Issuance Costs	(3)	(4)
Carrying Value	$ 493	$ 491
3.25% 2018 Senior Notes, due 2021
Debt Instrument [Line Items]
Notes payable, interest rate	3.25%	3.25%
Principal Amount	$ 300	$ 300
Fair Value of Interest Rate Swap	0	0
Unamortized (Discount) Premium	0	0
Unamortized Debt Issuance Costs	(1)	(2)
Carrying Value	$ 299	$ 298
4.25% 2018 Senior Notes, due 2029
Debt Instrument [Line Items]
Notes payable, interest rate	4.25%	4.25%
Principal Amount	$ 400	$ 400
Fair Value of Interest Rate Swap	0	0
Unamortized (Discount) Premium	(3)	(3)
Unamortized Debt Issuance Costs	(3)	(3)
Carrying Value	$ 394	$ 394
4.875% 2018 Senior Notes, due 2048
Debt Instrument [Line Items]
Notes payable, interest rate	4.875%	4.875%
Principal Amount	$ 400	$ 400
Fair Value of Interest Rate Swap	0	0
Unamortized (Discount) Premium	(7)	(7)
Unamortized Debt Issuance Costs	(4)	(4)
Carrying Value	$ 389	$ 389
0.950% 2019 Senior Note, due 2030
Debt Instrument [Line Items]
Notes payable, interest rate	0.95%
Principal Amount	$ 842
Fair Value of Interest Rate Swap	0
Unamortized (Discount) Premium	(3)
Unamortized Debt Issuance Costs	(6)
Carrying Value	$ 833

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

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