Long-term Debt - Summary of Long-term Debt (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Long-term debt, carrying amount	$ 16,471	$ 14,770
3.65% Senior Notes due 2023
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,496	1,495
3.90% Senior Notes due 2028
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,449	1,444
1.375% Guaranteed Notes due 2026
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,163
2.0% Guaranteed Notes due 2032
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,163
0.25% Notes due 2027
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,058	550
0.50% Notes due 2031
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,058	544
2.65% Senior Notes due 2030
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,250
2.40% Senior Notes due 2022
Debt Instrument [Line Items]
Long-term debt, carrying amount	999	998
4.00% Senior Notes due 2025
Debt Instrument [Line Items]
Long-term debt, carrying amount	930	929
4.30% Senior Notes due 2029
Debt Instrument [Line Items]
Long-term debt, carrying amount	845	845
3.75% Senior Notes due 2024
Debt Instrument [Line Items]
Long-term debt, carrying amount	746	746
1.00% Guaranteed Notes due 2026
Debt Instrument [Line Items]
Long-term debt, carrying amount	704	665
2.65% Senior Notes due 2022
Debt Instrument [Line Items]
Long-term debt, carrying amount	598	598
0.00% Notes due 2024
Debt Instrument [Line Items]
Long-term debt, carrying amount	588	551
1.40% Senior Notes due 2025
Debt Instrument [Line Items]
Long-term debt, carrying amount	498
3.63% Senior Notes due 2022
Debt Instrument [Line Items]
Long-term debt, carrying amount	295	294
7.00% Notes due 2038
Debt Instrument [Line Items]
Long-term debt, carrying amount	206	208
5.95% Notes due 2041
Debt Instrument [Line Items]
Long-term debt, carrying amount	114	114
5.13% Notes due 2043
Debt Instrument [Line Items]
Long-term debt, carrying amount	99	99
4.00% Notes due 2023
Debt Instrument [Line Items]
Long-term debt, carrying amount	80	81
3.70% Notes due 2024
Debt Instrument [Line Items]
Long-term debt, carrying amount	55	55
3.30% Senior Notes due 2021
Debt Instrument [Line Items]
Long-term debt, carrying amount		1,597
4.20% Senior Notes due 2021
Debt Instrument [Line Items]
Long-term debt, carrying amount		600
Other
Debt Instrument [Line Items]
Long-term debt, carrying amount		135
Commercial paper borrowings
Debt Instrument [Line Items]
Long-term debt, carrying amount	$ 1,077	$ 2,222