Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Activities:
Net income	$ 5,364	$ 5,460	$ 4,644
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation expense	255	226	233
Amortization expense	1,149	1,203	1,053
Stock-based compensation expense	636	845	638
Deferred income taxes	(2,098)	289	(82)
Net gains from equity securities	(1,241)	(115)	0
Up-front and milestone expense related to collaborative and other arrangements	4,346	0	0
In-process research and development impairment	800	820	0
Write-downs for slow moving and excess raw material and work in process inventory	547	440	0
Other	184	171	304
Changes in operating assets and liabilities:
Accounts receivable, net	(218)	480	754
Inventories	(95)	(310)	(253)
Prepaid expenses and other	(307)	903	358
Accounts payable	(61)	(39)	(430)
Income taxes payable	272	(1,459)	5,497
Accrued liabilities	(389)	(514)	(818)
Net cash provided by operating activities	9,144	8,400	11,898
Investing Activities:
Purchases of marketable debt securities	(30,455)	(10,233)	(23,314)
Proceeds from sales of marketable debt securities	7,523	1,522	10,440
Proceeds from maturities of marketable debt securities	22,398	24,336	7,821
Up-front and milestone payments related to collaborative and other arrangements	(4,301)	0	0
Purchases of equity securities	(1,773)	(156)	0
Acquisitions, net of cash acquired	0	0	(10,426)
Capital expenditures	(825)	(924)	(590)
Other	(384)	(190)	0
Net cash (used in) provided by investing activities	(7,817)	14,355	(16,069)
Financing Activities:
Proceeds from debt financing, net of issuance costs	0	0	8,985
Proceeds from issuances of common stock	209	289	234
Repurchases of common stock	(1,749)	(2,900)	(954)
Repayments of debt and other obligations	(2,750)	(6,250)	(1,811)
Payment of dividends	(3,222)	(2,971)	(2,731)
Other	(122)	(486)	(330)
Net cash (used in) provided by financing activities	(7,634)	(12,318)	3,393
Effect of exchange rate changes on cash and cash equivalents	(2)	(85)	137
Net change in cash and cash equivalents	(6,309)	10,352	(641)
Cash and cash equivalents at beginning of period	17,940	7,588	8,229
Cash and cash equivalents at end of period	11,631	17,940	7,588
Supplemental disclosure of cash flow information:
Interest paid, net of amounts capitalized	982	1,070	1,038
Income taxes paid	$ 1,793	$ 3,198	$ 3,342