Debt - Long Term Debt (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Nov. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Total debt	$ 13,812		$ 15,312
Commercial paper	0		600
Less: unamortized discounts and issuance costs	(1,158)		(1,208)
Total debt, net	12,654		14,104
Less: current portion	(1,250)		(1,500)
Long-term debt, net	$ 11,404		12,604
4.25% due 2019
Debt Instrument [Line Items]
Interest rate	4.25%	4.25%
Total debt	$ 0		900
2.50% due 2020
Debt Instrument [Line Items]
Interest rate	2.50%
Total debt	$ 1,250		1,250
3.35% due 2021
Debt Instrument [Line Items]
Interest rate	3.35%
Total debt	$ 900		900
3.10% due 2023
Debt Instrument [Line Items]
Interest rate	3.10%
Total debt	$ 500		500
2.90% due 2025
Debt Instrument [Line Items]
Interest rate	2.90%
Total debt	$ 750		750
3.55% due 2026
Debt Instrument [Line Items]
Interest rate	3.55%
Total debt	$ 2,000		2,000
3.60% due 2035
Debt Instrument [Line Items]
Interest rate	3.60%
Total debt	$ 500		500
4.50% and 6.15% due 2036
Debt Instrument [Line Items]
Long-term debt maturity year	2036
Total debt	$ 1,054		1,054
4.50% and 6.15% due 2036 | Minimum
Debt Instrument [Line Items]
Interest rate	4.50%
4.50% and 6.15% due 2036 | Maximum
Debt Instrument [Line Items]
Interest rate	6.15%
4.07% due 2042
Debt Instrument [Line Items]
Interest rate	4.07%
Total debt	$ 1,336		1,336
3.80% due 2045
Debt Instrument [Line Items]
Interest rate	3.80%
Total debt	$ 1,000		1,000
4.70% due 2046
Debt Instrument [Line Items]
Interest rate	4.70%
Total debt	$ 1,326		1,326
4.09% due 2052
Debt Instrument [Line Items]
Interest rate	4.09%
Total debt	$ 1,578		1,578
Other notes with rates from 4.85% to 9.13%, due 2022 to 2041
Debt Instrument [Line Items]
Total debt	$ 1,618		$ 1,618
Other notes with rates from 4.85% to 9.13%, due 2022 to 2041 | Minimum
Debt Instrument [Line Items]
Interest rate	4.85%
Other notes with rates from 4.85% to 9.13%, due 2022 to 2041 | Maximum
Debt Instrument [Line Items]
Interest rate	8.50%