Accounting Policies - Additional Information (Details) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2022 USD ($)	Dec. 31, 2022 USD ($) Segment	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Accounting Policies [Line items]
Number of reportable segments | Segment		1
Restricted amounts held in escrow-current	$ 3.9	$ 3.9	$ 4.1
Percentage of workforce covered by collective bargaining agreements		82.00%
Allowance for doubtful accounts	23.7	$ 23.7	13.2
Rerate reserve as a reduction to accounts receivable	22.5	22.5	14.1
Operating revenue	32.3	$ 32.3	$ 41.3
Risk-free rate for maturities of workers' compensation claims		2.80%	0.40%	0.50%
Risk-free rate for property damage and liability claims		2.70%	0.20%	0.50%
Depreciation		$ 136.9	$ 137.1	$ 133.0
Sale of terminal	31.0
Gain from sale of terminal	28.1
Cargo Claims And Other Insurance Related Amounts
Accounting Policies [Line items]
Undiscounted amount	$ 16.4	$ 16.4	$ 17.1