Reclassifications Out of Accumulated Other Comprehensive Income (Loss) - Reclassifications (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Other income, net		$ 140	$ 79	$ 128	$ 128
Amortization, net, included in General and administrative and costs benefitting inventory/production process		1,655	1,711	4,635	4,867
Costs applicable to sales	[1]	1,133	1,185	3,171	3,328
Interest expense, net		(81)	(89)	(248)	(276)
Income (loss) before income and mining tax and other items		437	25	1,158	260
Tax benefit (expense)		151	(47)	496	(22)
Net income (loss)		285	75	662	268
Marketable securities adjustments
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Net of tax				100
Pension and other post-retirement benefit adjustments
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Total before tax		8	3	22	10
Tax benefit (expense)		3	1	7	3
Net of tax		5	2	15	7
Accumulated defined benefit pension plans adjustment, amortization
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Total before tax		5	3	19	10
Accumulated defined benefit pension plans adjustment, settlement
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Total before tax		3		3
Changes in fair value of cash flow hedge instruments
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Net of tax				40
Reclassification Out of Accumulated Other Comprehensive Income
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Net of tax		50	6	155	(5)
Reclassification Out of Accumulated Other Comprehensive Income | Marketable securities adjustments
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Income (loss) before income and mining tax and other items		28	3	100	(1)
Tax benefit (expense)					1
Net income (loss)		28	3	100
Reclassification Out of Accumulated Other Comprehensive Income | Accumulated net marketable securities adjustments - sale of marketable securities
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Other income, net				(1)	(5)
Reclassification Out of Accumulated Other Comprehensive Income | Accumulated net marketable securities adjustments - Impairment of marketable securities
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Other income, net		28	3	101	4
Reclassification Out of Accumulated Other Comprehensive Income | Changes in fair value of cash flow hedge instruments
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Income (loss) before income and mining tax and other items		23	2	57	(17)
Tax benefit (expense)		(6)	(1)	(17)	5
Net income (loss)		17	1	40	(12)
Reclassification Out of Accumulated Other Comprehensive Income | Operating cash flow hedges | Changes in fair value of cash flow hedge instruments
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Other income, net		(1)		(2)
Costs applicable to sales		19	(3)	45	(31)
Reclassification Out of Accumulated Other Comprehensive Income | Interest rate contracts | Changes in fair value of cash flow hedge instruments
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Interest expense, net		$ 5	$ 5	$ 14	$ 14

[1] Excludes Depreciation and amortization and Reclamation and remediation.