CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
CURRENT ASSETS
Cash and cash equivalents	$ 124,652	$ 120,772
Short-term investments	54,669	56,401
Accounts receivable, less allowances (2018 – $7,837; 2017 – $7,657)	289,366	279,074
Other accounts receivable, less allowances (2018 – $936; 2017 – $921)	19,262	19,491
Prepaid expenses	24,891	22,183
Prepaid and refundable income taxes	10,267	12,296
Other	9,029	12,132
TOTAL CURRENT ASSETS	532,136	522,349
PROPERTY, PLANT AND EQUIPMENT
Land and structures	338,346	344,224
Revenue equipment	790,685	793,523
Service, office, and other equipment	189,055	179,950
Software	132,088	129,589
Leasehold improvements	8,948	8,888
TOTAL PROPERTY, PLANT AND EQUIPMENT, GROSS	1,459,122	1,456,174
Less allowances for depreciation and amortization	884,959	865,010
PROPERTY, PLANT AND EQUIPMENT, net	574,163	591,164
GOODWILL	108,320	108,320
INTANGIBLE ASSETS, net	72,336	73,469
DEFERRED INCOME TAXES	6,095	5,965
OTHER LONG-TERM ASSETS	65,033	64,374
TOTAL ASSETS	1,358,083	1,365,641
CURRENT LIABILITIES
Accounts payable	139,830	129,099
Income taxes payable	93	324
Accrued expenses	202,656	211,237
Current portion of long-term debt	56,057	61,930
TOTAL CURRENT LIABILITIES	398,636	402,590
LONG-TERM DEBT, less current portion	196,425	206,989
PENSION AND POSTRETIREMENT LIABILITIES	36,984	39,827
OTHER LONG-TERM LIABILITIES	12,320	15,616
DEFERRED INCOME TAXES	48,244	49,157
STOCKHOLDERS' EQUITY
Common stock, $0.01 par value, authorized 70,000,000 shares; issued 2018: 28,498,971 shares; 2017: 28,495,628 shares	285	285
Additional paid-in capital	321,265	319,436
Retained earnings	450,267	438,379
Treasury stock, at cost, 2018: 2,857,460 shares; 2017: 2,851,578 shares	(86,265)	(86,064)
Accumulated other comprehensive loss	(20,078)	(20,574)
TOTAL STOCKHOLDERS' EQUITY	665,474	651,462
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 1,358,083	$ 1,365,641