EMPLOYEE BENEFIT PLANS - NET PENSION EXPENSE (Details) - Qualified Defined Benefit [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 13	$ 13
Interest cost	14	19
Expected return on assets	31	28
Recognized actuarial loss (gain)	(9)	(9)
Wages and Benefits [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Net pension expense	13	13
Nonoperating Income (Expense) [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Net pension expense	$ (8)	$ 0