EMPLOYEE BENEFIT PLANS - NET PENSION EXPENSE (Details) - Qualified Defined Benefit [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 12	$ 10	$ 36	$ 30
Interest cost	20	19	59	55
Expected return on assets	(27)	(27)	(80)	(80)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	(1)	(1)	(1)	(1)
Recognized actuarial loss (gain)	9	7	25	20
Wages and Benefits [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Net pension expense	12	10	36	30
Nonoperating Income (Expense) [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Net pension expense	$ 1	$ (2)	$ 3	$ (6)