Consolidated Statements of Cash Flows (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Operating Activities
Net income	$ 1,502	$ 2,634
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	888	712
Pension and other postretirement benefits, net	3	119
Deferred income taxes	22	425
Net gain on disposal of assets	(3)	(178)
Equity method investments, net	(4)	13
Changes in the fair value of derivative instruments	(54)	8
Changes in:
Current receivables	(974)	360
Inventories	(1,330)	(555)
Current accounts payable and accrued liabilities	2,028	(1,160)
All other, net	(28)	71
Net cash provided by operating activities	2,050	2,449
Investing activities:
Additions to property, plant and equipment	(733)	(966)
Acquisitions	(1,515)	(190)
Disposal of assets	12	52
Investments—acquisition, loans and contributions	(113)	(26)
Investments-redemptions and repayments	76	94
All other, net	22	3
Net cash used in investing activities	(2,251)	(1,033)
Financing activities:
Long-term debt—repayments	(16)	(12)
Debt issuance costs	(2)	(6)
Issuance of common stock	37	54
Common stock repurchased	(2,341)	(850)
Dividends paid	(358)	(291)
Distributions to noncontrolling interests	(15)	0
Tax settlement with Marathon Oil Corporation	39	0
All other, net	15	(3)
Net cash used in financing activities	(2,641)	(1,108)
Net increase (decrease) in cash and cash equivalents	(2,842)	308
Cash and cash equivalents at beginning of period	4,860	3,079
Cash and cash equivalents at end of period	$ 2,018	$ 3,387