Indebtedness - Fair Value and Carrying Value of Long-Term Debt (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Carrying Amount	$ 7,476	$ 6,422
Estimated Fair Value	8,118	7,256
4.50% 2012 Senior Notes, due 2022
Debt Instrument [Line Items]
Carrying Amount	507	512
Estimated Fair Value	$ 515	$ 530
Notes payable, interest rate	4.50%	4.50%
4.875% 2013 Senior Notes, due 2024
Debt Instrument [Line Items]
Carrying Amount	$ 493	$ 498
Estimated Fair Value	$ 545	$ 562
Notes payable, interest rate	4.875%	4.875%
5.25% 2014 Senior Notes, due 2044
Debt Instrument [Line Items]
Carrying Amount	$ 594	$ 598
Estimated Fair Value	$ 808	$ 828
Notes payable, interest rate	5.25%	5.25%
1.75% 2015 Senior Notes, due 2027
Debt Instrument [Line Items]
Carrying Amount	$ 577	$ 610
Estimated Fair Value	$ 629	$ 674
Notes payable, interest rate	1.75%	1.75%
2.625% 2017 Senior Notes, due 2023
Debt Instrument [Line Items]
Carrying Amount	$ 507	$ 510
Estimated Fair Value	$ 514	$ 522
Notes payable, interest rate	2.625%	2.625%
3.25% 2017 Senior Notes, due 2028
Debt Instrument [Line Items]
Carrying Amount	$ 509	$ 524
Estimated Fair Value	$ 544	$ 561
Notes payable, interest rate	3.25%	3.25%
4.25% 2018 Senior Notes, due 2029
Debt Instrument [Line Items]
Carrying Amount	$ 396	$ 394
Estimated Fair Value	$ 460	$ 480
Notes payable, interest rate	4.25%	4.25%
4.875% 2018 Senior Notes, due 2048
Debt Instrument [Line Items]
Carrying Amount	$ 390	$ 390
Estimated Fair Value	$ 526	$ 544
Notes payable, interest rate	4.875%	4.875%
0.950% Senior Notes Due 2030
Debt Instrument [Line Items]
Carrying Amount	$ 862	$ 909
Estimated Fair Value	$ 898	$ 974
Notes payable, interest rate	0.95%	0.95%
3.75% 2020 Senior Notes, due 2025
Debt Instrument [Line Items]
Carrying Amount	$ 690	$ 693
Estimated Fair Value	$ 761	$ 785
Notes payable, interest rate	3.75%	3.75%
3.25% 2020 Senior Notes, due 2050
Debt Instrument [Line Items]
Carrying Amount	$ 293	$ 293
Estimated Fair Value	$ 309	$ 329
Notes payable, interest rate	3.25%	3.25%
2.55% 2020 Senior Notes, due 2060
Debt Instrument [Line Items]
Carrying Amount	$ 491	$ 491
Estimated Fair Value	$ 437	$ 467
Notes payable, interest rate	2.55%	2.55%
2.00% 2021 Senior Note, due 2031
Debt Instrument [Line Items]
Carrying Amount	$ 587
Estimated Fair Value	$ 588
Notes payable, interest rate	2.00%
2.75% 2021 Senior Note, due 2041
Debt Instrument [Line Items]
Carrying Amount	$ 580
Estimated Fair Value	$ 584
Notes payable, interest rate	2.75%

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

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