Long-Term Debt - Long-Term Debt Obligations (Details) - USD ($)	Oct. 04, 2017	Sep. 30, 2017	Aug. 31, 2017	Aug. 28, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2014	Nov. 30, 2012
Debt Instrument [Line Items]
Total debt		$ 25,847,000,000			$ 8,838,000,000
Less current portion of long-term debt		(1,037,000,000)			(1,056,000,000)
Face value of long-term debt		24,810,000,000			7,782,000,000
Senior Notes
Debt Instrument [Line Items]
Face amount of notes			$ 16,000,000,000	$ 1,000,000,000			$ 6,000,000,000	$ 3,000,000,000
Total debt		$ 25,300,000,000
Senior Notes | 1.200% Notes due on November 29, 2017 (1)
Debt Instrument [Line Items]
Stated interest rate		1.20%
Total debt		$ 1,000,000,000			1,000,000,000
Effective interest rates		1.38%
Senior Notes | 2.600% Notes due on December 5, 2019 (2)
Debt Instrument [Line Items]
Stated interest rate		2.60%
Total debt		$ 1,000,000,000			1,000,000,000
Effective interest rates		2.73%
Senior Notes | 1.900% Notes due on August 21, 2020 (3)
Debt Instrument [Line Items]
Stated interest rate		1.90%
Total debt		$ 1,000,000,000
Effective interest rates		2.16%
Senior Notes | 3.300% Notes due on December 5, 2021 (2)
Debt Instrument [Line Items]
Stated interest rate		3.30%
Total debt		$ 1,000,000,000			1,000,000,000
Effective interest rates		3.43%
Senior Notes | 2.500% Notes due on November 29, 2022 (1)
Debt Instrument [Line Items]
Stated interest rate		2.50%
Total debt		$ 1,250,000,000			1,250,000,000
Effective interest rates		2.66%
Senior Notes | 2.400% Notes due on February 22, 2023 (3)
Debt Instrument [Line Items]
Stated interest rate		2.40%
Total debt		$ 1,000,000,000
Effective interest rates		2.56%
Senior Notes | 2.800% Notes due on August 22, 2024 (3)
Debt Instrument [Line Items]
Stated interest rate		2.80%
Total debt		$ 2,000,000,000
Effective interest rates		2.95%
Senior Notes | 3.800% Notes due on December 5, 2024 (2)
Debt Instrument [Line Items]
Stated interest rate		3.80%
Total debt		$ 1,250,000,000			1,250,000,000
Effective interest rates		3.90%
Senior Notes | 5.200% Notes due on December 3, 2025 (4)
Debt Instrument [Line Items]
Stated interest rate		5.20%
Total debt		$ 1,000,000,000
Effective interest rates		3.03%
Senior Notes | 3.150% Notes due on August 22, 2027 (3)
Debt Instrument [Line Items]
Stated interest rate		3.15%
Total debt		$ 3,500,000,000
Effective interest rates		3.25%
Senior Notes | 4.800% Notes due on December 5, 2034 (2)
Debt Instrument [Line Items]
Stated interest rate		4.80%
Total debt		$ 1,250,000,000			1,250,000,000
Effective interest rates		4.92%
Senior Notes | 3.875% Notes due on August 22, 2037 (3)
Debt Instrument [Line Items]
Stated interest rate		3.875%
Total debt		$ 2,750,000,000
Effective interest rates		3.94%
Senior Notes | 4.950% Notes due on December 5, 2044 (2)
Debt Instrument [Line Items]
Stated interest rate		4.95%
Total debt		$ 1,500,000,000			1,500,000,000
Effective interest rates		5.11%
Senior Notes | 4.050% Notes due on August 22, 2047 (3)
Debt Instrument [Line Items]
Stated interest rate		4.05%
Total debt		$ 3,500,000,000
Effective interest rates		4.13%
Senior Notes | 4.250% Notes due on August 22, 2057 (3)
Debt Instrument [Line Items]
Stated interest rate		4.25%
Total debt		$ 2,250,000,000
Effective interest rates		4.33%
Credit Facility | Revolving Credit Facility
Debt Instrument [Line Items]
Total debt		$ 550,000,000			495,000,000
Credit Facility | October 2016 Revolving Credit Facility | Revolving Credit Facility
Debt Instrument [Line Items]
Maximum Borrowing Capacity						$ 500,000,000
Other Long-term Debt
Debt Instrument [Line Items]
Total debt		$ 47,000,000			$ 93,000,000
Subsequent Event [Member] | Credit Facility | October 2016 Revolving Credit Facility | Revolving Credit Facility
Debt Instrument [Line Items]
Maximum Borrowing Capacity	$ 600,000,000