CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
CURRENT ASSETS
Cash and cash equivalents	$ 215,590	$ 262,226
Short-term investments	44,865	67,842
Accounts receivable, less allowances (2024 - $8,788; 2023 - $10,346)	429,511	430,122
Other accounts receivable, less allowances (2024 - $654; 2023 - $731)	11,846	52,124
Prepaid expenses	31,835	37,034
Prepaid and refundable income taxes	22,555	24,319
Other	11,011	11,116
TOTAL CURRENT ASSETS	767,213	884,783
PROPERTY, PLANT AND EQUIPMENT
Land and structures	507,194	460,068
Revenue equipment	1,143,985	1,126,055
Service, office, and other equipment	326,633	319,466
Software	177,933	173,354
Leasehold improvements	27,675	24,429
TOTAL PROPERTY, PLANT AND EQUIPMENT, Gross	2,183,420	2,103,372
Less allowances for depreciation and amortization	1,212,381	1,188,548
PROPERTY, PLANT AND EQUIPMENT, net	971,039	914,824
GOODWILL	304,753	304,753
INTANGIBLE ASSETS, net	94,740	101,150
OPERATING RIGHT-OF-USE ASSETS	186,779	169,999
DEFERRED INCOME TAXES	9,974	8,140
OTHER LONG-TERM ASSETS	74,031	101,445
TOTAL ASSETS	2,408,529	2,485,094
CURRENT LIABILITIES
Accounts payable	222,303	214,004
Income taxes payable		10,410
Accrued expenses	332,258	378,029
Current portion of long-term debt	58,615	66,948
Current portion of operating lease liabilities	32,674	32,172
TOTAL CURRENT LIABILITIES	645,850	701,563
LONG-TERM DEBT, less current portion	144,972	161,990
OPERATING LEASE LIABILITIES, less current portion	185,637	176,621
POSTRETIREMENT LIABILITIES, less current portion	13,264	13,319
CONTINGENT CONSIDERATION	104,070	92,900
OTHER LONG-TERM LIABILITIES	37,606	40,553
DEFERRED INCOME TAXES	45,592	55,785
STOCKHOLDERS' EQUITY
Common stock, $0.01 par value, authorized 70,000,000 shares; issued 2024: 30,399,853 shares; 2023: 30,024,125 shares	304	300
Additional paid-in capital	324,645	340,961
Retained earnings	1,311,549	1,272,584
Treasury stock, at cost, 2024: 6,711,805 shares; 2023: 6,460,137 shares	(407,433)	(375,806)
Accumulated other comprehensive income	2,473	4,324
TOTAL STOCKHOLDERS' EQUITY	1,231,538	1,242,363
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 2,408,529	$ 2,485,094