Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Cash flows from operating activities:
Net income	$ 30,059	$ 59,897	$ 46,959	$ 226,514
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and amortization of property, equipment, and intangibles			595,322	540,555
Gain on sale of property and equipment			(21,839)	(46,628)
Impairments	1,008	0	10,867	0
Deferred income taxes			(21,569)	9,587
Non-cash lease expense			137,768	68,778
Loss (gain) on equity securities			11,562	(2,100)
Other adjustments to reconcile net income to net cash provided by operating activities			(3,684)	46,224
Increase (decrease) in cash resulting from changes in:
Trade receivables			39,612	84,149
Income tax receivable			19,624	(1,237)
Accounts payable			(57,066)	(10,495)
Accrued liabilities and claims accrual			(135,189)	26,599
Operating lease liabilities			(146,973)	(68,140)
Other assets and liabilities			49,347	(304)
Net cash provided by operating activities			524,741	873,502
Cash flows from investing activities:
Proceeds from maturities of held-to-maturity investments			530	3,620
Purchases of held-to-maturity investments			0	(30)
Proceeds from sale of property and equipment, including assets held for sale			183,589	214,234
Purchases of property and equipment			(592,081)	(852,677)
Expenditures on assets held for sale			(312)	(785)
Net cash, restricted cash, and equivalents invested in acquisitions			(185,491)	(458,288)
Other cash flows from investing activities			(25,255)	5,896
Net cash used in investing activities			(619,020)	(1,088,030)
Cash flows from financing activities:
Repayments of finance leases and long-term debt			(214,881)	(81,354)
Proceeds from long-term debt			150,000	250,000
Borrowings on revolving lines of credit, net			160,000	257,000
Borrowings under accounts receivable securitization			28,800	25,000
Repayments of accounts receivable securitization			(96,600)	(82,000)
Proceeds from common stock issued			4,177	4,200
Dividends paid			(78,256)	(68,550)
Other cash flows from financing activities			(7,735)	(18,206)
Net cash (used in) provided by financing activities			(54,495)	286,090
Net (decrease) increase in cash, restricted cash, and equivalents			(148,774)	71,562
Cash, restricted cash, and equivalents at beginning of period			469,686	385,345	$ 385,345
Cash, restricted cash, and equivalents at end of period	$ 320,912	456,907	320,912	456,907	$ 469,686
Cash paid during the period for:
Interest			130,680	84,361
Income taxes			10,382	38,455
Other Significant Noncash Transactions [Line Items]
Equipment acquired included in accounts payable			39,522	19,639
Contingent consideration associated with acquisitions and investments			0	174,107
U.S. Xpress assumed equity awards		$ 1,462	0	1,462
Conversion of note receivable to equity investment			0	12,107
Right-of-use assets obtained in exchange for operating lease liabilities			58,767	41,888
Property and equipment obtained in exchange for finance lease liabilities			190,298	70,051
Financing provided to independent contractors for equipment sold
Other Significant Noncash Transactions [Line Items]
Other non-cash investing and financing activities			1,715	4,285
Transfers from property and equipment to assets held for sale [Member]
Other Significant Noncash Transactions [Line Items]
Other non-cash investing and financing activities			89,794	136,453
Noncontrolling Interest Associated With Acquisition
Other Significant Noncash Transactions [Line Items]
Other non-cash investing and financing activities			0	5,178
Property and equipment obtained in exchange for debt and finance lease liabilities from operating lease liabilities
Other Significant Noncash Transactions [Line Items]
Property and equipment obtained in exchange for finance lease liabilities			20,025	0
Acquisitions [Member]
Other Significant Noncash Transactions [Line Items]
Right-of-use assets obtained in exchange for operating lease liabilities through acquisitions			$ 12,400	$ 0