Employee Benefit Plans - Benefit Plan Assets Measured at Fair Value on Recurring Basis (Details) - Recurring - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Benefit plan assets by asset class
Benefit plan assets	$ 20,046	$ 16,600
Level 1 and Level 2
Benefit plan assets by asset class
Benefit plan assets	7,393	6,173
Level 1 and Level 2 | Cash equivalents
Benefit plan assets by asset class
Benefit plan assets	4,487	3,664
Level 1 and Level 2 | Equities and equity-related instruments
Benefit plan assets by asset class
Benefit plan assets	1,195	1,120
Level 1 and Level 2 | Fixed income and fixed income-related instruments
Benefit plan assets by asset class
Benefit plan assets	1,048	882
Level 1 and Level 2 | Delta common stock
Benefit plan assets by asset class
Benefit plan assets	407	507
Level 1 and Level 2 | Real assets
Benefit plan assets by asset class
Benefit plan assets	256	0
Level 1
Benefit plan assets by asset class
Benefit plan assets	3,900	1,873
Level 1 | Cash equivalents
Benefit plan assets by asset class
Benefit plan assets	2,390	305
Level 1 | Equities and equity-related instruments
Benefit plan assets by asset class
Benefit plan assets	1,034	1,061
Level 1 | Fixed income and fixed income-related instruments
Benefit plan assets by asset class
Benefit plan assets	69	0
Level 1 | Delta common stock
Benefit plan assets by asset class
Benefit plan assets	407	507
Level 1 | Real assets
Benefit plan assets by asset class
Benefit plan assets	0	0
Level 2
Benefit plan assets by asset class
Benefit plan assets	3,493	4,300
Level 2 | Cash equivalents
Benefit plan assets by asset class
Benefit plan assets	2,097	3,359
Level 2 | Equities and equity-related instruments
Benefit plan assets by asset class
Benefit plan assets	161	59
Level 2 | Fixed income and fixed income-related instruments
Benefit plan assets by asset class
Benefit plan assets	979	882
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	256	0
NAV
Benefit plan assets by asset class
Benefit plan assets	$ 12,653	$ 10,427