EMPLOYEE BENEFIT PLANS - Benefit Plan Assets Measured at Fair Value on Recurring Basis (Details) - Recurring - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Benefit plan assets by asset class
Benefit plan assets	$ 16,166	$ 15,641
Level 1 and Level 2
Benefit plan assets by asset class
Benefit plan assets	4,749	3,312
Level 1 and Level 2 | Fixed income and fixed income-related instruments
Benefit plan assets by asset class
Benefit plan assets	2,158	1,443
Level 1 and Level 2 | Cash equivalents
Benefit plan assets by asset class
Benefit plan assets	1,156	894
Level 1 and Level 2 | Equities and equity-related instruments
Benefit plan assets by asset class
Benefit plan assets	769	445
Level 1 and Level 2 | Delta common stock
Benefit plan assets by asset class
Benefit plan assets	419	343
Level 1 and Level 2 | Real assets
Benefit plan assets by asset class
Benefit plan assets	247	187
Level 1
Benefit plan assets by asset class
Benefit plan assets	1,848	1,486
Level 1 | Fixed income and fixed income-related instruments
Benefit plan assets by asset class
Benefit plan assets	300	77
Level 1 | Cash equivalents
Benefit plan assets by asset class
Benefit plan assets	471	629
Level 1 | Equities and equity-related instruments
Benefit plan assets by asset class
Benefit plan assets	647	420
Level 1 | Delta common stock
Benefit plan assets by asset class
Benefit plan assets	419	343
Level 1 | Real assets
Benefit plan assets by asset class
Benefit plan assets	11	17
Level 2
Benefit plan assets by asset class
Benefit plan assets	2,901	1,826
Level 2 | Fixed income and fixed income-related instruments
Benefit plan assets by asset class
Benefit plan assets	1,858	1,366
Level 2 | Cash equivalents
Benefit plan assets by asset class
Benefit plan assets	685	265
Level 2 | Equities and equity-related instruments
Benefit plan assets by asset class
Benefit plan assets	122	25
Level 2 | Delta common stock
Benefit plan assets by asset class
Benefit plan assets	0	0
Level 2 | Real assets
Benefit plan assets by asset class
Benefit plan assets	236	170
NAV
Benefit plan assets by asset class
Benefit plan assets	$ 11,417	$ 12,329