CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
CURRENT ASSETS
Cash and cash equivalents	$ 127,058	$ 76,620
Short-term investments	76,802	48,339
Accounts receivable, less allowances (2022 - $15,991; 2021 - $13,226)	659,672	582,344
Other accounts receivable, less allowances (2022 - $703; 2021 - $690)	18,612	13,094
Prepaid expenses	32,353	40,104
Prepaid and refundable income taxes	10,310	9,654
Other	10,750	5,898
TOTAL CURRENT ASSETS	935,557	776,053
PROPERTY, PLANT AND EQUIPMENT
Land and structures	356,149	350,694
Revenue equipment	993,008	980,283
Service, office, and other equipment	276,965	251,085
Software	179,195	175,989
Leasehold improvements	20,189	16,931
TOTAL PROPERTY, PLANT AND EQUIPMENT, Gross	1,825,506	1,774,982
Less allowances for depreciation and amortization	1,115,887	1,079,061
PROPERTY, PLANT AND EQUIPMENT, net	709,619	695,921
GOODWILL	299,075	300,337
INTANGIBLE ASSETS, net	120,145	126,580
OPERATING RIGHT-OF-USE ASSETS	124,086	106,686
DEFERRED INCOME TAXES	5,655	5,470
OTHER LONG-TERM ASSETS	99,569	101,629
TOTAL ASSETS	2,293,706	2,112,676
CURRENT LIABILITIES
Accounts payable	346,051	311,401
Income taxes payable	17,110	12,087
Accrued expenses	304,425	305,851
Current portion of long-term debt	56,049	50,615
Current portion of operating lease liabilities	24,534	22,740
TOTAL CURRENT LIABILITIES	748,169	702,694
LONG-TERM DEBT, less current portion	169,356	174,917
OPERATING LEASE LIABILITIES, less current portion	104,253	88,835
POSTRETIREMENT LIABILITIES, less current portion	16,694	16,733
OTHER LONG-TERM LIABILITIES	132,930	135,537
DEFERRED INCOME TAXES	59,092	64,893
STOCKHOLDERS' EQUITY
Common stock, $0.01 par value, authorized 70,000,000 shares; issued 2022: 29,614,798 shares, 2021: 29,359,597 shares	296	294
Additional paid-in capital	340,035	318,033
Retained earnings	968,417	801,314
Treasury stock, at cost, 2022: 5,109,030 shares; 2021: 4,492,514 shares	(250,510)	(194,273)
Accumulated other comprehensive income	4,974	3,699
TOTAL STOCKHOLDERS' EQUITY	1,063,212	929,067
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 2,293,706	$ 2,112,676