Long-term Debt - Summary of Long-term Debt (Detail) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Long-term debt, carrying amount	$ 16,763	$ 14,770
3.65% Senior Notes due 2023
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,495	1,495
3.90% Senior Notes due 2028
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,447	1,444
1.375% Guaranteed Notes due 2026
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,119
2.0% Guaranteed Notes due 2032
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,119
0.25% Notes due 2027
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,008	550
0.50% Notes due 2031
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,008	544
4.00% Senior Notes due 2025
Debt Instrument [Line Items]
Long-term debt, carrying amount	929	929
2.40% Senior Notes due 2022
Debt Instrument [Line Items]
Long-term debt, carrying amount	999	998
2.65% Senior Notes due 2030
Debt Instrument [Line Items]
Long-term debt, carrying amount	892
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	671	665
3.30% Senior Notes due 2021
Debt Instrument [Line Items]
Long-term debt, carrying amount	664	1,597
0.00% Notes due 2024
Debt Instrument [Line Items]
Long-term debt, carrying amount	560	551
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	207	208
5.95% Notes due 2041
Debt Instrument [Line Items]
Long-term debt, carrying amount	114	114
2.65% Senior Notes due 2022
Debt Instrument [Line Items]
Long-term debt, carrying amount	598	598
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	81	81
3.70% Notes due 2024
Debt Instrument [Line Items]
Long-term debt, carrying amount	55	55
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	$ 1,812	$ 2,222