Financing arrangements (Long-term Borrowings) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Carrying values of long-term borrowings
Short-term loan	$ 0	$ 605
Total carrying value of debt	35,342	34,596
Less current portion	(1,152)	(4,403)
Total noncurrent debt	$ 34,190	$ 30,193
2.125% notes due 2017 (2.125% 2017 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note		2.125%
Carrying values of long-term borrowings
Notes payable, noncurrent		$ 1,250
Floating rate notes due 2017 [Member]
Carrying values of long-term borrowings
Notes payable, noncurrent		$ 600
1.25% notes due 2017 (1.25% 2017 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note		1.25%
Carrying values of long-term borrowings
Notes payable, noncurrent		$ 850
5.85% notes due 2017 (5.85% 2017 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note		5.85%
Carrying values of long-term borrowings
Notes payable, noncurrent		$ 1,100
6.15% notes due 2018 (6.15% 2018 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	6.15%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 500	500
4.375% euro-denominated notes due 2018 (4.375% 2018 euro Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	4.375%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 653	577
5.70% notes due 2019 (5.70% 2019 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	5.70%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 1,000	1,000
1.90% notes due 2019 (1.90% 2019 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	1.90%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 700
Floating rate notes due 2019 [Member]
Debt Instrument [Line Items]
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 550	250
2.20% notes due 2019 (2.20% 2019 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	2.20%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 1,400	1,400
2.125% euro-denominated notes due 2019 (2.125% 2019 euro Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	2.125%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 810	710
4.50% notes due 2020 (4.50% 2020 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	4.50%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 300	300
2.125% notes due 2020 (2.125% 2020 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	2.125%		2.125%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 750	750
Floating Rate Notes Due 2020 [Member]
Debt Instrument [Line Items]
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 300
2.20% notes due 2020 (2.20% 2020 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	2.20%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 700
3.45% notes due 2020 (3.45% 2020 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	3.45%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 900	900
4.10% notes due 2021 (4.10% 2021 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	4.10%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 1,000	$ 1,000
1.85% notes due 2021 (1.85% 2021 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	1.85%	1.85%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 750	$ 750
3.875% notes due 2021 (3.875% 2021 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	3.875%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 1,750	$ 1,750
1.25% notes due 2022 (1.25% 2022 euro Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	1.25%	1.25%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 1,501	$ 1,315
2.70% notes due 2022 (2.70% 2022 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	2.70%		2.70%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 500	500
2.65% notes due 2022 (2.65% 2022 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	2.65%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 1,500
3.625% notes due 2022 (3.625% 2022 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	3.625%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 750	$ 750
0.41% 2023 Swiss franc Bonds [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	0.41%	0.41%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 719	$ 687
2.25% notes due 2023 (2.25% 2023 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	2.25%	2.25%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 750	$ 750
3.625% notes due 2024 (3.625% 2024 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	3.625%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 1,400	1,400
3.125% notes due 2025 (3.125% 2025 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	3.125%		3.125%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 1,000	$ 1,000
2.00% 2026 euro Notes [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	2.00%	2.00%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 901	$ 789
2.60% notes due 2026 (2.60% 2026 notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	2.60%	2.60%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 1,250	$ 1,250
5.50% pound-sterling-denominated notes due 2026 (5.50% 2026 pound sterling Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	5.50%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 642	586
3.20% notes due 2027 (3.20% 2027 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	3.20%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 1,000
4.00% pound-sterling-denominated notes due 2029 (4.00% 2029 pound sterling Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	4.00%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 946	864
6.375% notes due 2037 (6.375% 2037 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	6.375%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 552	552
6.90% notes due 2038 (6.90% 2038 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	6.90%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 291	291
6.40% notes due 2039 (6.40% 2039 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	6.40%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 466	466
5.75% notes due 2040 (5.75% 2040 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	5.75%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 412	412
4.95% notes due 2041 (4.95% 2041 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	4.95%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 600	600
5.15% notes due 2041 (5.15% 2041 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	5.15%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 974	974
5.65% notes due 2042 (5.65% 2042 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	5.65%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 487	487
5.375% notes due 2043 (5.375% 2043 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	5.375%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 261	$ 261
4.40% notes due 2045 (4.40% 2045 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	4.40%	4.40%	4.40%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 2,250	$ 2,250
4.563% notes due 2048 (4.563% 2048 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	4.563%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Effective interest rate on note	6.30%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 1,415	1,415
4.663% notes due 2051 (4.663% 2051 Notes) [Member]
Debt Instrument [Line Items]
Stated contractual interest rate on note	4.663%
Percentage of principal amount of notes that may be paid upon occurrence of change in control triggering event	101.00%
Effective interest rate on note	5.60%
Carrying values of long-term borrowings
Notes payable, noncurrent	$ 3,541	3,541
Other notes due 2097 [Member]
Carrying values of long-term borrowings
Notes payable, noncurrent	100	100
Debt Securities Payable [Member]
Carrying values of long-term borrowings
Unamortized bond discounts and issuance costs	$ 929	$ 936
Minimum [Member] | Debt Securities Payable [Member]
Carrying values of long-term borrowings
Redemption period without payment of make whole amount	1 month
Maximum [Member] | Debt Securities Payable [Member]
Carrying values of long-term borrowings
Redemption period without payment of make whole amount	6 months