Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Activities:
Net income	$ 4,644	$ 13,488	$ 18,106
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation expense	233	177	161
Amortization expense	1,053	981	937
Stock-based compensation expense	638	380	382
Deferred income taxes	(82)	(119)	(393)
In-process research and development impairment	0	432	0
Other	304	162	562
Changes in operating assets and liabilities:
Accounts receivable, net	754	1,192	(1,397)
Inventories	(253)	(488)	(855)
Prepaid expenses and other	358	(520)	(90)
Accounts payable	(430)	47	226
Income taxes payable	5,497	1,010	269
Accrued liabilities	(818)	305	3,342
Net cash provided by operating activities	11,898	17,047	21,250
Investing Activities:
Purchases of marketable securities	(23,314)	(25,619)	(17,239)
Proceeds from sales of marketable securities	10,440	13,039	4,792
Proceeds from maturities of marketable securities	7,821	1,700	719
Other investments	0	(357)	0
Acquisitions, net of cash acquired	(10,426)	0	0
Capital expenditures	(590)	(748)	(747)
Net cash used in investing activities	(16,069)	(11,985)	(12,475)
Financing Activities:
Proceeds from debt financing, net of issuance costs	8,985	5,293	9,902
Proceeds from convertible note hedges	0	956	784
Proceeds from issuances of common stock	234	208	319
Repurchases of common stock	(954)	(11,001)	(10,002)
Repayments of debt and other obligations	(1,811)	(1,981)	(997)
Payments to settle warrants	0	(469)	(3,865)
Payment of dividends	(2,731)	(2,455)	(1,874)
Other	(330)	(276)	(151)
Net cash provided by (used in) financing activities	3,393	(9,725)	(5,884)
Effect of exchange rate changes on cash and cash equivalents	137	41	(67)
Net change in cash and cash equivalents	(641)	(4,622)	2,824
Cash and cash equivalents at beginning of period	8,229	12,851	10,027
Cash and cash equivalents at end of period	7,588	8,229	12,851
Supplemental disclosure of cash flow information:
Interest paid, net of amounts capitalized	1,038	885	529
Income taxes paid	$ 3,342	$ 2,436	$ 3,137