CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
CURRENT ASSETS
Cash and cash equivalents	$ 251,503	$ 158,264
Short-term investments	89,326	167,662
Accounts receivable, less allowances (2023 - $10,825; 2022 - $13,892)	469,490	517,494
Other accounts receivable, less allowances (2023 - $730; 2022 - $713)	10,984	11,016
Prepaid expenses	30,957	39,484
Prepaid and refundable income taxes	26,534	19,239
Current assets of discontinued operations		64,736
Other	11,342	11,888
TOTAL CURRENT ASSETS	890,136	989,783
PROPERTY, PLANT AND EQUIPMENT
Land and structures	430,263	401,840
Revenue equipment	1,094,183	1,038,832
Service, office, and other equipment	313,062	298,234
Software	169,434	167,164
Leasehold improvements	26,062	23,466
TOTAL PROPERTY, PLANT AND EQUIPMENT, Gross	2,033,004	1,929,536
Less allowances for depreciation and amortization	1,170,914	1,129,366
PROPERTY, PLANT AND EQUIPMENT, net	862,090	800,170
GOODWILL	304,753	304,753
INTANGIBLE ASSETS, net	104,288	113,733
OPERATING RIGHT-OF-USE ASSETS	164,082	166,515
DEFERRED INCOME TAXES	7,618	6,342
LONG-TERM ASSETS OF DISCONTINUED OPERATIONS		11,097
OTHER LONG-TERM ASSETS	104,479	101,893
TOTAL ASSETS	2,437,446	2,494,286
CURRENT LIABILITIES
Accounts payable	245,899	269,854
Income taxes payable	1,390	16,017
Accrued expenses	322,809	338,457
Current portion of long-term debt	66,862	66,252
Current portion of operating lease liabilities	31,414	26,225
Current liabilities of discontinued operations		51,665
TOTAL CURRENT LIABILITIES	668,374	768,470
LONG-TERM DEBT, less current portion	176,296	198,371
OPERATING LEASE LIABILITIES, less current portion	171,755	147,828
POSTRETIREMENT LIABILITIES, less current portion	12,167	12,196
LONG-TERM LIABILITIES OF DISCONTINUED OPERATIONS		781
CONTINGENT CONSIDERATION	99,200	112,000
OTHER LONG-TERM LIABILITIES	38,552	42,745
DEFERRED INCOME TAXES	50,369	60,494
STOCKHOLDERS' EQUITY
Common stock, $0.01 par value, authorized 70,000,000 shares; issued 2023: 30,017,658 shares; 2022: 29,758,716 shares	300	298
Additional paid-in capital	338,368	339,582
Retained earnings	1,226,640	1,088,693
Treasury stock, at cost, 2023: 6,217,885 shares; 2022: 5,529,383 shares	(350,161)	(284,275)
Accumulated other comprehensive income	5,586	7,103
TOTAL STOCKHOLDERS' EQUITY	1,220,733	1,151,401
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 2,437,446	$ 2,494,286