EMPLOYEE BENEFITS - Schedule of Net Periodic (Income) Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 3	$ 3	$ 3
Interest cost	46	48	48
Expected return on plan assets	(69)	(68)	(74)
Amortization of actuarial loss	18	16	15
Net periodic pension (income) cost	(2)	(1)	(8)
Qualified Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	3	3	3
Interest cost	42	44	44
Expected return on plan assets	(69)	(68)	(74)
Amortization of actuarial loss	16	14	13
Net periodic pension (income) cost	(8)	(7)	(14)
Non-Qualified Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0	0
Interest cost	4	4	4
Expected return on plan assets	0	0	0
Amortization of actuarial loss	2	2	2
Net periodic pension (income) cost	$ 6	$ 6	$ 6