CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
CURRENT ASSETS
Cash and cash equivalents	$ 187,286	$ 158,264
Short-term investments	153,116	167,662
Accounts receivable, less allowances (2023 - $11,318; 2022 - $13,892)	429,570	517,494
Other accounts receivable, less allowances (2023 - $721; 2022 - $713)	11,160	11,016
Prepaid expenses	33,244	39,484
Prepaid and refundable income taxes	39,230	19,239
Current assets of discontinued operations		64,736
Other	11,584	11,888
TOTAL CURRENT ASSETS	865,190	989,783
PROPERTY, PLANT AND EQUIPMENT
Land and structures	421,821	401,840
Revenue equipment	1,062,854	1,038,832
Service, office, and other equipment	309,952	298,234
Software	167,292	167,164
Leasehold improvements	26,240	23,466
TOTAL PROPERTY, PLANT AND EQUIPMENT, Gross	1,988,159	1,929,536
Less allowances for depreciation and amortization	1,159,626	1,129,366
PROPERTY, PLANT AND EQUIPMENT, net	828,533	800,170
GOODWILL	304,753	304,753
INTANGIBLE ASSETS, net	107,467	113,733
OPERATING RIGHT-OF-USE ASSETS	194,597	166,515
DEFERRED INCOME TAXES	6,918	6,342
LONG-TERM ASSETS OF DISCONTINUED OPERATIONS		11,097
OTHER LONG-TERM ASSETS	106,644	101,893
TOTAL ASSETS	2,414,102	2,494,286
CURRENT LIABILITIES
Accounts payable	245,998	269,854
Income taxes payable		16,017
Accrued expenses	299,339	338,457
Current portion of long-term debt	64,882	66,252
Current portion of operating lease liabilities	31,047	26,225
Current liabilities of discontinued operations		51,665
TOTAL CURRENT LIABILITIES	641,266	768,470
LONG-TERM DEBT, less current portion	168,105	198,371
OPERATING LEASE LIABILITIES, less current portion	174,145	147,828
POSTRETIREMENT LIABILITIES, less current portion	12,169	12,196
LONG-TERM LIABILITIES OF DISCONTINUED OPERATIONS		781
CONTINGENT CONSIDERATION	117,040	112,000
OTHER LONG-TERM LIABILITIES	37,314	42,745
DEFERRED INCOME TAXES	52,702	60,494
STOCKHOLDERS' EQUITY
Common stock, $0.01 par value, authorized 70,000,000 shares; issued 2023: 30,007,634 shares; 2022: 29,758,716 shares	300	298
Additional paid-in capital	335,397	339,582
Retained earnings	1,194,610	1,088,693
Treasury stock, at cost, 2023: 5,982,679 shares; 2022: 5,529,383 shares	(325,515)	(284,275)
Accumulated other comprehensive income	6,569	7,103
TOTAL STOCKHOLDERS' EQUITY	1,211,361	1,151,401
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 2,414,102	$ 2,494,286