PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS - Net Periodic Benefit Cost (Credit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost (credit)(2)	$ 0	$ (151)	$ 0
Recognition of curtailments, settlements and special termination benefits due to closures, restructuring or divestitures(1)	0	3	0
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	57	53	64
Interest cost	265	271	244
Expected return on plan assets	(476)	(467)	(439)
Amortization of actuarial loss	182	125	221
Amortization of prior service cost (credit)(2)	4	5	7
Recognition of curtailments, settlements and special termination benefits due to closures, restructuring or divestitures(1)	0	9	0
Other	0	0	0
Net periodic benefit cost (credit)	32	(4)	97
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	1	1
Interest cost	9	10	12
Expected return on plan assets	0	0	0
Amortization of actuarial loss	10	12	14
Amortization of prior service cost (credit)(2)	(9)	(161)	(23)
Recognition of curtailments, settlements and special termination benefits due to closures, restructuring or divestitures(1)	0	0	0
Other	0	(4)	0
Net periodic benefit cost (credit)	$ 10	(142)	4
Gain on postretirement plan amendment | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost (credit)(2)		(151)
Real Estate Divestiture | Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost		$ 2	$ 4