Accident and Workers' Compensation Insurance Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accident and Workers' Compensation Insurance Liabilities [Line Items]
Excess Insurance Coverage Limit	$ 80.0	$ 60.0
Workers compensation retention limit	1.0	1.0
Trust fund requirements	0.7
Trust Fund Balance	0.9	0.8
Debt Securities, Held-to-Maturity	0.3	0.8
Other Investments	0.6
Letters of Credit	13.5
Letter of credit due	0.0	0.0
Excess Insurance Variable Premium Coverage Minimum Claims	3.0
Excess Insurance Variable Premium Coverage Maximum Claims	10.0
Aggregate Self-Insurance Corridor	3.5	1.0
Auto Liability 50% Exposure Minimum [Member]		5.0
Auto Liability 50% Exposure Maximum [Member]		10.0
Auto liability retention limit maximum [Member]
Accident and Workers' Compensation Insurance Liabilities [Line Items]
Auto liability retention limit	$ 3.0	2.0	$ 2.0
Auto liability retention limit, Smith Transport		$ 0.5