Indebtedness - Summary of Total Indebtedness (Detail) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Principal Amount	$ 6,382	$ 6,430
Fair Value of Interest Rate Swap	32	56
Unamortized (Discount) Premium	(22)	(24)
Unamortized Debt Issuance Costs	(37)	(40)
Long term debt	$ 6,355	$ 6,422
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	10	14
Unamortized (Discount) Premium	0	(1)
Unamortized Debt Issuance Costs	0	(1)
Long term debt	$ 510	$ 512
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	(1)	(1)
Long term debt	$ 498	$ 498
5.25% 2014 Senior Notes, due 2044
Debt Instrument [Line Items]
Notes payable, interest rate	5.25%	5.25%
Principal Amount	$ 600	$ 600
Fair Value of Interest Rate Swap	0	0
Unamortized (Discount) Premium	3	3
Unamortized Debt Issuance Costs	(5)	(5)
Long term debt	$ 598	$ 598
1.75% 2015 Senior Notes, due 2027
Debt Instrument [Line Items]
Notes payable, interest rate	1.75%	1.75%
Principal Amount	$ 593	$ 612
Fair Value of Interest Rate Swap	0	0
Unamortized (Discount) Premium	0	0
Unamortized Debt Issuance Costs	(2)	(2)
Long term debt	$ 591	$ 610
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	9	12
Unamortized (Discount) Premium	0	0
Unamortized Debt Issuance Costs	(1)	(2)
Long term debt	$ 508	$ 510
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	18	31
Unamortized (Discount) Premium	(4)	(4)
Unamortized Debt Issuance Costs	(3)	(3)
Long term debt	$ 511	$ 524
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	(2)	(3)
Unamortized Debt Issuance Costs	(3)	(3)
Long term debt	$ 395	$ 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	(6)	(6)
Unamortized Debt Issuance Costs	(4)	(4)
Long term debt	$ 390	$ 390
0.950% Senior Notes Due 2030
Debt Instrument [Line Items]
Notes payable, interest rate	0.95%	0.95%
Principal Amount	$ 889	$ 918
Fair Value of Interest Rate Swap	0	0
Unamortized (Discount) Premium	(3)	(3)
Unamortized Debt Issuance Costs	(6)	(6)
Long term debt	$ 880	$ 909
3.75% 2020 Senior Notes, due 2025
Debt Instrument [Line Items]
Notes payable, interest rate	3.75%	3.75%
Principal Amount	$ 700	$ 700
Fair Value of Interest Rate Swap	(5)	(1)
Unamortized (Discount) Premium	(1)	(1)
Unamortized Debt Issuance Costs	(4)	(5)
Long term debt	$ 690	$ 693
3.25% 2020 Senior Notes, due 2050
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	(4)	(4)
Unamortized Debt Issuance Costs	(3)	(3)
Long term debt	$ 293	$ 293
2.55% 2020 Senior Notes, due 2060
Debt Instrument [Line Items]
Notes payable, interest rate	2.55%	2.55%
Principal Amount	$ 500	$ 500
Fair Value of Interest Rate Swap	0	0
Unamortized (Discount) Premium	(4)	(4)
Unamortized Debt Issuance Costs	(5)	(5)
Long term debt	$ 491	$ 491

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

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