Debt - Additional Information (Detail) - USD ($)				1 Months Ended		3 Months Ended	12 Months Ended
	Nov. 23, 2015	Oct. 09, 2015	Feb. 20, 2015	Sep. 25, 2016	May 31, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Repayment of long-term notes							$ 952,000,000
Interest payments							600,000,000	$ 375,000,000	$ 325,000,000
Repayment of line of credit facility								6,000,000,000
Repayment of commercial paper						$ 1,000,000,000
Borrowings under commercial paper						$ 0	$ 0	$ 0
Variable Interest Rate Swap | Designated as hedges
Debt Instrument [Line Items]
Aggregate notional amount of derivatives					$ 450,000,000
November 2015 Notes
Debt Instrument [Line Items]
Amount of issued debt	$ 7,000,000,000
Net proceeds from notes offering	6,900,000,000
1.85% due 2018
Debt Instrument [Line Items]
Amount of issued debt	$ 750,000,000
Long-term debt maturity year	2018						2018	2018
Interest Rate	1.85%					1.85%	1.85%	1.85%
Notes interest payment dates							May 23 and November 23 of each year
2.50% due 2020
Debt Instrument [Line Items]
Amount of issued debt	$ 1,250,000,000
Long-term debt maturity year	2020						2020	2020
Interest Rate	2.50%					2.50%	2.50%	2.50%
Notes interest payment dates							May 23 and November 23 of each year
3.10% due 2023
Debt Instrument [Line Items]
Amount of issued debt	$ 500,000,000
Long-term debt maturity year	2023						2023	2023
Interest Rate	3.10%					3.10%	3.10%	3.10%
Notes interest payment dates							January 15 and July 15 of each year
3.55% due 2026
Debt Instrument [Line Items]
Amount of issued debt	$ 2,000,000,000
Long-term debt maturity year	2026						2026	2026
Interest Rate	3.55%					3.55%	3.55%	3.55%
Notes interest payment dates							January 15 and July 15 of each year
2036 Notes
Debt Instrument [Line Items]
Amount of issued debt	$ 500,000,000
Long-term debt maturity year	2036
Interest Rate	4.50%
Notes interest payment dates							May 15 and November 15 of each year
4.70% due 2046
Debt Instrument [Line Items]
Amount of issued debt	$ 2,000,000,000
Long-term debt maturity year	2046						2046	2046
Interest Rate	4.70%					4.70%	4.70%	4.70%
Notes interest payment dates							May 15 and November 15 of each year
2.13% Long-term notes
Debt Instrument [Line Items]
Repayment of long-term notes				$ 500,000,000
Interest Rate				2.13%
7.65% Long-term notes
Debt Instrument [Line Items]
Repayment of long-term notes					$ 452,000,000
Interest Rate					7.65%
February 2015 Notes
Debt Instrument [Line Items]
Amount of issued debt			$ 2,250,000,000
Net proceeds from notes offering			2,210,000,000
Notes interest payment dates							March 1 and September 1 of each year
2.90% Due 2025
Debt Instrument [Line Items]
Amount of issued debt			$ 750,000,000
Long-term debt maturity year			2025				2025	2025
Interest Rate			2.90%			2.90%	2.90%	2.90%
3.60% Due 2035
Debt Instrument [Line Items]
Amount of issued debt			$ 500,000,000
Long-term debt maturity year			2035				2035	2035
Interest Rate			3.60%			3.60%	3.60%	3.60%
3.80% due 2045
Debt Instrument [Line Items]
Amount of issued debt			$ 1,000,000,000
Long-term debt maturity year			2045				2045	2045
Interest Rate			3.80%			3.80%	3.80%	3.80%
Unsecured Debt | Five Year Revolving Credit Facility
Debt Instrument [Line Items]
Line of credit facility		$ 2,500,000,000				$ 0	$ 0	$ 0
Line of credit facility expiration period		5 years
Line of credit facility extended expiration period		1 year
Line of credit facility expiration date		Oct. 09, 2020					Oct. 09, 2021
Terminated revolving credit facility		$ 1,500,000,000
Additional amount to increase credit facility, granted at banks' discretion		500,000,000
Unsecured Debt | Three Hundred And Sixty Four Day Revolving Credit Facility And Five Year Revolving Credit Facility
Debt Instrument [Line Items]
Line of credit facility		$ 7,000,000,000
Line of credit facility expiration period		364 days
Line of credit facility expiration date		Nov. 23, 2015
Line of credit facility, amount outstanding		$ 6,000,000,000
Repayment of line of credit facility	$ 6,000,000,000