EMPLOYEE BENEFIT PLANS - NET PENSION EXPENSE (Details) - Qualified Defined Benefit [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 10	$ 12	$ 21	$ 24
Interest cost	22	19	44	39
Expected return on assets	(23)	(26)	(47)	(53)
Recognized actuarial loss (gain)	9	8	18	16
Wages and Benefits [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Net pension expense	10	12	21	24
Nonoperating Income (Expense) [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Net pension expense	$ 8	$ 1	$ 15	$ 2