Long Term Debt (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Total debt	$ 15,294	$ 16,296
Less: unamortized discounts and issuance costs	(1,012)	(1,035)
Total debt, net	14,282	15,261
Less: current portion		(956)
Long-term debt, net	14,282	14,305
2.13% and 7.65% due 2016
Debt Instrument [Line Items]
Total debt		952
1.85% due 2018
Debt Instrument [Line Items]
Total debt	750	750
4.25% due 2019
Debt Instrument [Line Items]
Total debt	900	900
2.50% due 2020
Debt Instrument [Line Items]
Total debt	1,250	1,250
3.35% due 2021
Debt Instrument [Line Items]
Total debt	900	900
3.10% due 2023
Debt Instrument [Line Items]
Total debt	500	500
2.90% Due 2025
Debt Instrument [Line Items]
Total debt	750	750
3.55% due 2026
Debt Instrument [Line Items]
Total debt	2,000	2,000
3.60% Due 2035
Debt Instrument [Line Items]
Total debt	500	500
4.50% and 6.15% due 2036
Debt Instrument [Line Items]
Total debt	1,152	1,152
4.85% due 2041
Debt Instrument [Line Items]
Total debt	600	600
4.07% due 2042
Debt Instrument [Line Items]
Total debt	1,336	1,336
3.80% due 2045
Debt Instrument [Line Items]
Total debt	1,000	1,000
4.70% due 2046
Debt Instrument [Line Items]
Total debt	2,000	2,000
Other notes with rates from 5.50% to 8.50%, due 2023 to 2040
Debt Instrument [Line Items]
Total debt	$ 1,656	$ 1,706