Long-term Debt - Summary of Long-term Debt (Detail) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Long-term debt, carrying amount	$ 15,834	$ 16,036
3.65% Senior Notes due 2023
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,496	1,496
3.90% Senior Notes due 2028
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,452	1,450
2.65% Senior Notes due 2030
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,250	1,250
1.375% Guaranteed Notes due 2026
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,173	1,221
2.0% Guaranteed Notes due 2032
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,167	1,214
0.25% Notes due 2027
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,057	1,100
0.50% Notes due 2031
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,056	1,099
2.40% Senior Notes due 2022
Debt Instrument [Line Items]
Long-term debt, carrying amount	999	999
4.00% Senior Notes due 2025
Debt Instrument [Line Items]
Long-term debt, carrying amount	930	930
4.30% Senior Notes due 2029
Debt Instrument [Line Items]
Long-term debt, carrying amount	845	846
3.75% Senior Notes due 2024
Debt Instrument [Line Items]
Long-term debt, carrying amount	747	746
1.00% Guaranteed Notes due 2026
Debt Instrument [Line Items]
Long-term debt, carrying amount	703	736
0.00% Notes due 2024
Debt Instrument [Line Items]
Long-term debt, carrying amount	588	611
2.65% Senior Notes due 2022
Debt Instrument [Line Items]
Long-term debt, carrying amount	599	598
1.40% Senior Notes due 2025
Debt Instrument [Line Items]
Long-term debt, carrying amount	498	498
3.63% Senior Notes due 2022
Debt Instrument [Line Items]
Long-term debt, carrying amount	295	295
7.00% Notes due 2038
Debt Instrument [Line Items]
Long-term debt, carrying amount	205	206
5.95% Notes due 2041
Debt Instrument [Line Items]
Long-term debt, carrying amount	113	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	80
3.70% Notes due 2024
Debt Instrument [Line Items]
Long-term debt, carrying amount	55	55
Commercial paper borrowings
Debt Instrument [Line Items]
Long-term debt, carrying amount	$ 427	$ 393