Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Activities:
Net income	$ 5,460	$ 4,644	$ 13,488
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation expense	226	233	177
Amortization expense	1,203	1,053	981
Stock-based compensation expense	845	638	380
Deferred income taxes	289	(82)	(119)
In-process research and development impairment	820	0	432
Inventory reserve for excess raw materials	440	0	0
Other	56	304	162
Changes in operating assets and liabilities:
Accounts receivable, net	480	754	1,192
Inventories	(310)	(253)	(488)
Prepaid expenses and other	903	358	(520)
Accounts payable	(39)	(430)	47
Income taxes payable	(1,459)	5,497	1,010
Accrued liabilities	(514)	(818)	305
Net cash provided by operating activities	8,400	11,898	17,047
Investing Activities:
Purchases of marketable securities	(10,233)	(23,314)	(25,619)
Proceeds from sales of marketable securities	1,522	10,440	13,039
Proceeds from maturities of marketable securities	24,336	7,821	1,700
Other investments	(346)	0	(357)
Acquisitions, net of cash acquired	0	(10,426)	0
Capital expenditures	(924)	(590)	(748)
Net cash provided by (used in) investing activities	14,355	(16,069)	(11,985)
Financing Activities:
Proceeds from debt financing, net of issuance costs	0	8,985	5,293
Proceeds from convertible note hedges	0	0	956
Proceeds from issuances of common stock	289	234	208
Repurchases of common stock	(2,900)	(954)	(11,001)
Repayments of debt and other obligations	(6,250)	(1,811)	(1,981)
Payments to settle warrants	0	0	(469)
Payment of dividends	(2,971)	(2,731)	(2,455)
Other	(486)	(330)	(276)
Net cash provided by (used in) financing activities	(12,318)	3,393	(9,725)
Effect of exchange rate changes on cash and cash equivalents	(85)	137	41
Net change in cash and cash equivalents	10,352	(641)	(4,622)
Cash and cash equivalents at beginning of period	7,588	8,229	12,851
Cash and cash equivalents at end of period	17,940	7,588	8,229
Supplemental disclosure of cash flow information:
Interest paid, net of amounts capitalized	1,070	1,038	885
Income taxes paid	$ 3,198	$ 3,342	$ 2,436