Accident and Workers' Compensation Insurance Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Accident and Workers' Compensation Insurance Liabilities [Line Items]
Excess Insurance Coverage Limit	$ 60.0
Trust fund requirements	0.7
Debt Securities, Held-to-maturity	0.8	$ 1.5
Letters of Credit	15.4
Letter of credit due	0.0	$ 0.0
Excess Insurance Coverage Minimum Claims			$ 3.0
Excess Insurance Coverage Maximum Claims			10.0
Aggregate Self-Insurance Corridor	1.0
Aggregate Self-Insurance Corridor Claims Minimum [Member]	2.0
Aggregate Self-Insurance Corridor Claims Maximum [Member]	3.0
Auto Liability 50% Exposure Minimum [Member]	5.0
Auto Liability 50% Exposure Maximum [Member]	10.0
Auto liability retention limit minimum [Member]
Accident and Workers' Compensation Insurance Liabilities [Line Items]
Auto liability retention limit	1.0		0.1
Auto liability retention limit, Smith Transport	0.1
Auto liability retention limit maximum [Member]
Accident and Workers' Compensation Insurance Liabilities [Line Items]
Auto liability retention limit	2.0		2.0
Auto liability retention limit, Smith Transport	0.5
workers compensation retention limit minimum [Member]
Accident and Workers' Compensation Insurance Liabilities [Line Items]
Workers compensation retention limit	1.0		0.5
workers compensation retention limit maximum [Member]
Accident and Workers' Compensation Insurance Liabilities [Line Items]
Workers compensation retention limit	$ 1.0		$ 1.0