Financial Instruments and Fair Value Measures - Basis Used to Measure Assets and Liabilities Carried at Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Assets
Equity securities	$ 2,528	$ 2,050
Foreign currency contracts - asset position	23	225
Liabilities
Foreign currency contracts - liability position	550	376
Fair Value Measurements Recurring
Assets
Cash and equivalents	9,303	5,100
Debt securities	2,524
Equity securities	4	1,974
Equity securities		76
Total assets	11,854	8,389
Liabilities
Interest rate hedges	401	338
Contingent consideration	4,534	4,213
Total liabilities	5,084	4,589
Fair Value Measurements Recurring | Foreign Currency Contract
Assets
Foreign currency contracts - asset position	23	225
Liabilities
Foreign currency contracts - liability position	149	38
Fair Value Measurements Recurring | Bank Time Deposits
Assets
Time deposits		1,014
Fair Value Measurements Recurring | Quoted prices in active markets for identical assets (Level 1)
Assets
Cash and equivalents	849	1,191
Debt securities	0
Equity securities	4	0
Equity securities		76
Total assets	853	1,267
Liabilities
Contingent consideration	0	0
Fair Value Measurements Recurring | Significant other observable inputs (Level 2)
Assets
Cash and equivalents	8,454	3,909
Debt securities	2,524
Equity securities		1,974
Equity securities		0
Total assets	11,001	7,122
Liabilities
Interest rate hedges	401	338
Contingent consideration	0	0
Total liabilities	550	376
Fair Value Measurements Recurring | Significant other observable inputs (Level 2) | Foreign Currency Contract
Assets
Foreign currency contracts - asset position	23	225
Liabilities
Foreign currency contracts - liability position	149	38
Fair Value Measurements Recurring | Significant other observable inputs (Level 2) | Bank Time Deposits
Assets
Time deposits		1,014
Fair Value Measurements Recurring | Significant unobservable Inputs (Level 3)
Assets
Debt securities	0
Liabilities
Contingent consideration	4,534	4,213
Total liabilities	$ 4,534	$ 4,213