CONTINGENCIES (Environmental Obligations) (Details) site in Thousands, $ in Millions		3 Months Ended	12 Months Ended
	Jan. 31, 2017 USD ($) divisions	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) site state project	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Site Contingency [Line Items]
Number of remediation projects | project			100
Number of US States with remediation projects | state			26
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of year			$ 1,221	$ 1,215	$ 1,174
Accretion Expense			84	81	78
Additions			241	26	33
Reductions			(43)	(43)	(3)
Spending			(64)	(58)	(67)
Balance at end of year			1,439	1,221	1,215
Less current portion			(134)	(129)	(100)
Long-term portion			1,305	$ 1,092	$ 1,115
Estimated environmental cash payments (on an undiscounted and unescalated basis) [Abstract]
2018			134
2019			132
2020			117
2021			119
2022			88
Thereafter			2,700
Estimated environmental obligations on a discounted basis			1,300
Estimated environmental obligations on an undiscounted and unescalated			$ 3,300
Number of site surveys being performed to mining claims | site			5
Environmental Loss Contingency, Number of Uranium Sites on Tribal Lands | divisions	94
Value of Consent Decree, Uranium Mines on Tribal Lands	$ 600
Remediation work related to Uranium mines, amount to be contributed by the U.S. Government	$ 335
Uranium mine remediation work, program term, in years	20 years
Minimum
Estimated environmental cash payments (on an undiscounted and unescalated basis) [Abstract]
Estimated environmental obligations on an undiscounted and unescalated			$ 2,800
Maximum
Estimated environmental cash payments (on an undiscounted and unescalated basis) [Abstract]
Estimated environmental obligations on an undiscounted and unescalated			3,700
Pinal Creek, AZ; Newtown Creek, NY; Smelter Sites in Arizona, Indiana, Kansas, Missouri, New Jersey, Oklahoma, Pennsylvania; and Uranium Mining in Wester United States
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at end of year			1,300
Newtown Creek
Accrual for Environmental Loss Contingencies [Roll Forward]
Additions			138
Borough of Carteret
Accrual for Environmental Loss Contingencies [Roll Forward]
Additions			$ 59
Uranium Mining Sites
Accrual for Environmental Loss Contingencies [Roll Forward]
Reductions		$ (41)