Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 1,979	$ 7,722	$ 6,939
Depreciation and amortization	1,955	2,105	2,108
Stock-based compensation expense	329	311	322
Deferred income taxes	(1,330)	183	(607)
Other items, net	334	32	(146)
Changes in operating assets and liabilities, net of acquisitions:
Trade receivables, net	(58)	(214)	(420)
Inventories	133	(80)	481
Other assets	(24)	(128)	155
Accounts payable	424	(44)	(12)
Accrued income taxes, net	523	(301)	509
Long-term tax liability	6,681	445	409
Other liabilities	231	323	(7)
Net cash provided by operating activities	11,177	10,354	9,731
Cash flows from investing activities:
Purchases of property, plant and equipment	(664)	(738)	(594)
Cash paid for acquisitions, net of cash acquired	(19)	0	(359)
Purchases of marketable securities	(33,607)	(28,094)	(25,977)
Proceeds from sales of marketable securities	24,240	17,958	18,029
Proceeds from maturities of marketable securities	6,174	2,459	3,527
Proceeds from sales of property, plant and equipment	11	78	274
Other	(159)	(321)	(447)
Net cash used in investing activities	(4,024)	(8,658)	(5,547)
Cash flows from financing activities:
Net proceeds from issuance of debt	4,476	7,318	3,465
Repayment of debt	(4,405)	(3,725)	(2,400)
Repurchases of common stock	(3,160)	(2,965)	(1,867)
Dividends paid	(3,365)	(2,998)	(2,396)
Settlement of contingent consideration obligations	0	0	(253)
Withholding taxes arising from shares withheld for share-based payments	(191)	(260)	(401)
Other	51	31	81
Net cash used in financing activities	(6,594)	(2,599)	(3,771)
Increase (decrease) in cash and cash equivalents	559	(903)	413
Cash and cash equivalents at beginning of year	3,241	4,144	3,731
Cash and cash equivalents at end of year	$ 3,800	$ 3,241	$ 4,144