Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) Segment	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jan. 01, 2019 USD ($)
Accounting Policies [Line items]
Number of reportable segments | Segment	1
Restricted amounts held in escrow-current	$ 38,700,000	$ 0
Allowance for doubtful accounts	13,800,000	11,400,000
Rerate reserve as a reduction to accounts receivable	12,600,000	7,900,000
Deferred revenue	$ 31,900,000	$ 25,200,000
Risk-free rate for maturities of workers' compensation claims	0.50%	2.00%	2.60%
Risk-free rate for property damage and liability claims	0.50%	2.10%	2.50%
Depreciation	$ 133,000,000.0	$ 150,500,000	$ 145,900,000
Acquisition of property and equipment	140,600,000	143,200,000	$ 145,400,000
Operating lease right-of-use assets	276,000,000.0	386,000,000.0		$ 378,800,000
Operating lease liability	286,800,000	367,100,000		378,800,000
Lease deposits				25,400,000
Operating lease liabilities	172,600,000	246,300,000		$ 25,400,000
Cargo Claims And Other Insurance Related Amounts
Accounting Policies [Line items]
Undiscounted amount	$ 11,100,000	$ 13,700,000
Accounting Standards Update 2014-09
Accounting Policies [Line items]
Change in accounting principle, ASU adopted	true
Change in accounting principle, ASU adoption date	Jan. 01, 2018
Change in accounting principle, ASU, immaterial effect	true
Accounting Standards Update 2016-02
Accounting Policies [Line items]
Change in accounting principle, ASU adopted	true
Change in accounting principle, ASU adoption date	Jan. 01, 2019
Accounting Standards Update 2018-14
Accounting Policies [Line items]
Change in accounting principle, ASU adopted	true
Change in accounting principle, ASU adoption date	Dec. 31, 2020
Change in accounting principle, ASU, immaterial effect	true
Workforce Subject to Collective Bargaining Arrangements | Labor Force Concentration Risk
Accounting Policies [Line items]
Percentage of workforce subject to collective bargaining agreements	79.00%