Accrued Workers' Compensation Costs - Summary of Workers' Compensation Loss Reserve Activity (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Total accrued costs, beginning of period	$ 199	$ 205	$ 198	$ 205
Incurred
Current year	16	18	33	33
Prior years	(15)	(12)	(20)	(15)
Total incurred	1	6	13	18
Paid
Current year	(2)	(2)	(2)	(3)
Prior years	(9)	(11)	(20)	(22)
Total paid	(11)	(13)	(22)	(25)
Total accrued costs, end of period	$ 189	$ 198	$ 189	$ 198