EMPLOYEE BENEFIT PLANS - NET PENSION EXPENSE (Details) - Qualified Defined Benefit [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 12	$ 10
Interest cost	20	18
Expected return on assets	(27)	(27)
Recognized actuarial loss (gain)	8	7
Operating Expense [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Net pension expense	12	10
Nonoperating Income (Expense) [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Net pension expense	$ 1	$ (2)