Borrowings - Schedule of Long-term Debt Instruments (Details) € in Millions, $ in Millions, £ in Billions	Dec. 31, 2017 USD ($)	Dec. 31, 2017 GBP (£)	Dec. 31, 2017 EUR (€)	Jan. 01, 2017 USD ($)	Jan. 01, 2017 GBP (£)	Jan. 01, 2017 EUR (€)
Debt Instrument [Line Items]
Effective interest rate	3.19%	3.19%	3.19%	3.33%	3.33%	3.33%
Less current portion	$ 1,500			$ 1,700
Total long-term debt	30,675			22,442
Carrying (Reported) Amount, Fair Value Disclosure
Debt Instrument [Line Items]
Long-term Debt	32,174			24,146
Less current portion	1,499			1,704
Total long-term debt	$ 30,675			$ 22,442
5.55% Debentures due 2017
Debt Instrument [Line Items]
Effective interest rate	0.00%	0.00%	0.00%	5.55%	5.55%	5.55%
Long-term Debt	$ 0			$ 1,000
Stated interest rate (as a percent)				5.55%	5.55%	5.55%
1.125% Notes due 2017
Debt Instrument [Line Items]
Effective interest rate	0.00%	0.00%	0.00%	1.15%	1.15%	1.15%
Long-term Debt	$ 0			$ 699
Stated interest rate (as a percent)				1.125%	1.125%	1.125%
5.15% Debentures due 2018
Debt Instrument [Line Items]
Effective interest rate	5.18%	5.18%	5.18%	5.18%	5.18%	5.18%
Long-term Debt	$ 900			$ 899
Stated interest rate (as a percent)	5.15%	5.15%	5.15%	5.15%	5.15%	5.15%
1.65% Notes due 2018
Debt Instrument [Line Items]
Effective interest rate	1.70%	1.70%	1.70%	1.70%	1.70%	1.70%
Long-term Debt	$ 597			$ 600
Stated interest rate (as a percent)	1.65%	1.65%	1.65%	1.65%	1.65%	1.65%
4.75% Notes due 2019 (1B Euro 1.1947)(2)/(1B Euro 1.0449)(3)
Debt Instrument [Line Items]
Effective interest rate	5.83%	5.83%	5.83%	5.83%	5.83%	5.83%
Long-term Debt	$ 1,192			$ 1,041
Stated interest rate (as a percent)	4.75%	4.75%	4.75%	4.75%	4.75%	4.75%
Debt Instrument, Face Amount | €			€ 1,000			€ 1,000
Foreign Currency Exchange Rate, Translation	1.1947	1.1947	1.1947	1.0449	1.0449	1.0449
1.875% Notes due 2019
Debt Instrument [Line Items]
Effective interest rate	1.93%	1.93%	1.93%	1.93%	1.93%	1.93%
Long-term Debt	$ 496			$ 499
Stated interest rate (as a percent)	1.875%	1.875%	1.875%	1.875%	1.875%	1.875%
0.89% Notes due 2019
Debt Instrument [Line Items]
Effective interest rate	1.75%	1.75%	1.75%	1.20%	1.20%	1.20%
Long-term Debt	$ 300			$ 299
Stated interest rate (as a percent)	0.89%	0.89%	0.89%	0.89%	0.89%	0.89%
1.125% Notes due 2019
Debt Instrument [Line Items]
Effective interest rate	1.13%	1.13%	1.13%	1.13%	1.13%	1.13%
Long-term Debt	$ 699			$ 699
Stated interest rate (as a percent)	1.125%	1.125%	1.125%	1.125%	1.125%	1.125%
3% Zero Coupon Convertible Subordinated Debentures due 2020
Debt Instrument [Line Items]
Effective interest rate	3.00%	3.00%	3.00%	3.00%	3.00%	3.00%
Long-term Debt	$ 60			$ 84
Stated interest rate (as a percent)	3.00%	3.00%	3.00%	3.00%	3.00%	3.00%
2.95% Debentures due 2020
Debt Instrument [Line Items]
Effective interest rate	3.15%	3.15%	3.15%	3.15%	3.15%	3.15%
Long-term Debt	$ 547			$ 546
Stated interest rate (as a percent)	2.95%	2.95%	2.95%	2.95%	2.95%	2.95%
1.950% Notes due 2020
Debt Instrument [Line Items]
Effective interest rate	1.99%	1.99%	1.99%	0.00%	0.00%	0.00%
Long-term Debt	$ 499			$ 0
Stated interest rate (as a percent)	1.95%	1.95%	1.95%
3.55% Notes due 2021
Debt Instrument [Line Items]
Effective interest rate	3.67%	3.67%	3.67%	3.67%	3.67%	3.67%
Long-term Debt	$ 448			$ 447
Stated interest rate (as a percent)	3.55%	3.55%	3.55%	3.55%	3.55%	3.55%
2.45% Notes due 2021
Debt Instrument [Line Items]
Effective interest rate	2.48%	2.48%	2.48%	2.48%	2.48%	2.48%
Long-term Debt	$ 349			$ 348
Stated interest rate (as a percent)	2.45%	2.45%	2.45%	2.45%	2.45%	2.45%
1.65% Notes due 2021
Debt Instrument [Line Items]
Effective interest rate	1.65%	1.65%	1.65%	1.65%	1.65%	1.65%
Long-term Debt	$ 998			$ 997
Stated interest rate (as a percent)	1.65%	1.65%	1.65%	1.65%	1.65%	1.65%
0.250% Notes due 2022 (1B Euro 1.1947)(2)/(1B Euro 1.0449)(3)
Debt Instrument [Line Items]
Effective interest rate	0.26%	0.26%	0.26%	0.26%	0.26%	0.26%
Long-term Debt	$ 1,191			$ 1,041
Stated interest rate (as a percent)	0.25%	0.25%	0.25%	0.25%	0.25%	0.25%
Debt Instrument, Face Amount | €			€ 1,000			€ 0
Foreign Currency Exchange Rate, Translation	1.1947	1.1947	1.1947	1.0449	1.0449	1.0449
2.25% Notes due 2022
Debt Instrument [Line Items]
Effective interest rate	2.31%	2.31%	2.31%	0.00%	0.00%	0.00%
Long-term Debt	$ 995			$ 0
Stated interest rate (as a percent)	2.25%	2.25%	2.25%
6.73% Debentures due 2023
Debt Instrument [Line Items]
Effective interest rate	6.73%	6.73%	6.73%	6.73%	6.73%	6.73%
Long-term Debt	$ 250			$ 249
Stated interest rate (as a percent)	6.73%	6.73%	6.73%	6.73%	6.73%	6.73%
3.375% Notes due 2023
Debt Instrument [Line Items]
Effective interest rate	3.17%	3.17%	3.17%	3.17%	3.17%	3.17%
Long-term Debt	$ 806			$ 807
Stated interest rate (as a percent)	3.375%	3.375%	3.375%	3.375%	3.375%	3.375%
2.05% Notes due 2023
Debt Instrument [Line Items]
Effective interest rate	2.09%	2.09%	2.09%	2.09%	2.09%	2.09%
Long-term Debt	$ 498			$ 497
Stated interest rate (as a percent)	2.05%	2.05%	2.05%	2.05%	2.05%	2.05%
0.650% Notes due 2024 (750MM Euro 1.1947)(2)/(750MM Euro 1.0449)(3)
Debt Instrument [Line Items]
Effective interest rate	0.68%	0.68%	0.68%	0.68%	0.68%	0.68%
Long-term Debt	$ 891			$ 779
Stated interest rate (as a percent)	0.65%	0.65%	0.65%	0.65%	0.65%	0.65%
Debt Instrument, Face Amount | €			€ 750			€ 750
Foreign Currency Exchange Rate, Translation	1.1947	1.1947	1.1947	1.0449	1.0449	1.0449
5.50% Notes due 2024 (500MM GBP 1.3444)(2)/(500MM GBP 1.2237)(3)
Debt Instrument [Line Items]
Effective interest rate	6.75%	6.75%	6.75%	6.75%	6.75%	6.75%
Long-term Debt	$ 666			$ 605
Stated interest rate (as a percent)	5.50%	5.50%	5.50%	5.50%	5.50%	5.50%
Debt Instrument, Face Amount | £		£ 0.5			£ 0.5
Foreign Currency Exchange Rate, Translation	1.3444	1.3444	1.3444	1.2237	1.2237	1.2237
2.625% Notes due 2025
Debt Instrument [Line Items]
Effective interest rate	2.63%	2.63%	2.63%	0.00%	0.00%	0.00%
Long-term Debt	$ 747			$ 0
Stated interest rate (as a percent)	2.625%	2.625%	2.625%
2.45% Notes due 2026
Debt Instrument [Line Items]
Effective interest rate	2.47%	2.47%	2.47%	2.47%	2.47%	2.47%
Long-term Debt	$ 1,990			$ 1,989
Stated interest rate (as a percent)	2.45%	2.45%	2.45%	2.45%	2.45%	2.45%
2.95% Notes due 2027
Debt Instrument [Line Items]
Effective interest rate	2.96%	2.96%	2.96%	0.00%	0.00%	0.00%
Long-term Debt	$ 995			$ 0
Stated interest rate (as a percent)	2.95%	2.95%	2.95%
1.150% Notes due 2028 (750MM Euro 1.1947)(2)/(750MM Euro 1.0449)(3)
Debt Instrument [Line Items]
Effective interest rate	1.21%	1.21%	1.21%	1.21%	1.21%	1.21%
Long-term Debt	$ 887			$ 775
Stated interest rate (as a percent)	1.15%	1.15%	1.15%	1.15%	1.15%	1.15%
Debt Instrument, Face Amount | €			€ 750			€ 750
Foreign Currency Exchange Rate, Translation	1.1947	1.1947	1.1947	1.0449	1.0449	1.0449
2.900% Notes due 2028
Debt Instrument [Line Items]
Effective interest rate	2.91%	2.91%	2.91%	0.00%	0.00%	0.00%
Long-term Debt	$ 1,492			$ 0
Stated interest rate (as a percent)	2.90%	2.90%	2.90%
6.95% Notes due 2029
Debt Instrument [Line Items]
Effective interest rate	7.14%	7.14%	7.14%	7.14%	7.14%	7.14%
Long-term Debt	$ 296			$ 296
Stated interest rate (as a percent)	6.95%	6.95%	6.95%	6.95%	6.95%	6.95%
4.95% Debentures due 2033
Debt Instrument [Line Items]
Effective interest rate	4.95%	4.95%	4.95%	4.95%	4.95%	4.95%
Long-term Debt	$ 498			$ 497
Stated interest rate (as a percent)	4.95%	4.95%	4.95%	4.95%	4.95%	4.95%
4.375% Notes due 2033
Debt Instrument [Line Items]
Effective interest rate	4.24%	4.24%	4.24%	4.24%	4.24%	4.24%
Long-term Debt	$ 856			$ 857
Stated interest rate (as a percent)	4.375%	4.375%	4.375%	4.375%	4.375%	4.375%
1.650% Notes due 2035 (1.5B Euro 1.1947)(2)/(1.5B Euro 1.0449)(3)
Debt Instrument [Line Items]
Effective interest rate	1.68%	1.68%	1.68%	1.68%	1.68%	1.68%
Long-term Debt	$ 1,774			$ 1,549
Stated interest rate (as a percent)	1.65%	1.65%	1.65%	1.65%	1.65%	1.65%
Debt Instrument, Face Amount | €			€ 1,500			€ 1,500
Foreign Currency Exchange Rate, Translation	1.1947	1.1947	1.1947	1.0449	1.0449	1.0449
3.55% Notes due 2036
Debt Instrument [Line Items]
Effective interest rate	3.59%	3.59%	3.59%	3.59%	3.59%	3.59%
Long-term Debt	$ 987			$ 987
Stated interest rate (as a percent)	3.55%	3.55%	3.55%	3.55%	3.55%	3.55%
5.95% Notes due 2037
Debt Instrument [Line Items]
Effective interest rate	5.99%	5.99%	5.99%	5.99%	5.99%	5.99%
Long-term Debt	$ 991			$ 990
Stated interest rate (as a percent)	5.95%	5.95%	5.95%	5.95%	5.95%	5.95%
3.625% Notes due 2037
Debt Instrument [Line Items]
Effective interest rate	3.64%	3.64%	3.64%	0.00%	0.00%	0.00%
Long-term Debt	$ 1,486			$ 0
Stated interest rate (as a percent)	3.625%	3.625%	3.625%
5.85% Debentures due 2038
Debt Instrument [Line Items]
Effective interest rate	5.85%	5.85%	5.85%	5.85%	5.85%	5.85%
Long-term Debt	$ 696			$ 695
Stated interest rate (as a percent)	5.85%	5.85%	5.85%	5.85%	5.85%	5.85%
3.400% Notes due 2038
Debt Instrument [Line Items]
Effective interest rate	3.42%	3.42%	3.42%	0.00%	0.00%	0.00%
Long-term Debt	$ 990			$ 0
Stated interest rate (as a percent)	3.40%	3.40%	3.40%
4.50% Debentures due 2040
Debt Instrument [Line Items]
Effective interest rate	4.63%	4.63%	4.63%	4.63%	4.63%	4.63%
Long-term Debt	$ 538			$ 537
Stated interest rate (as a percent)	4.50%	4.50%	4.50%	4.50%	4.50%	4.50%
4.85% Notes due 2041
Debt Instrument [Line Items]
Effective interest rate	4.89%	4.89%	4.89%	4.89%	4.89%	4.89%
Long-term Debt	$ 296			$ 296
Stated interest rate (as a percent)	4.85%	4.85%	4.85%	4.85%	4.85%	4.85%
4.50% Notes due 2043
Debt Instrument [Line Items]
Effective interest rate	4.52%	4.52%	4.52%	4.52%	4.52%	4.52%
Long-term Debt	$ 495			$ 495
Stated interest rate (as a percent)	4.50%	4.50%	4.50%	4.50%	4.50%	4.50%
3.70% Notes due 2046
Debt Instrument [Line Items]
Effective interest rate	3.74%	3.74%	3.74%	3.74%	3.74%	3.74%
Long-term Debt	$ 1,971			$ 1,970
Stated interest rate (as a percent)	3.70%	3.70%	3.70%	3.70%	3.70%	3.70%
3.75% Notes due 2047
Debt Instrument [Line Items]
Effective interest rate	3.76%	3.76%	3.76%	0.00%	0.00%	0.00%
Long-term Debt	$ 990			$ 0
Stated interest rate (as a percent)	3.75%	3.75%	3.75%
3.500% Notes due 2048
Debt Instrument [Line Items]
Effective interest rate	3.52%	3.52%	3.52%	0.00%	0.00%	0.00%
Long-term Debt	$ 742			$ 0
Stated interest rate (as a percent)	3.50%	3.50%	3.50%
Other
Debt Instrument [Line Items]
Effective interest rate	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%
Long-term Debt	$ 75			$ 77