CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
CURRENT ASSETS
Cash and cash equivalents	$ 177,436	$ 120,772
Short-term investments	75,879	56,401
Accounts receivable, less allowances (2018 – $7,475; 2017 – $7,657)	323,212	279,074
Other accounts receivable, less allowances (2018 – $975; 2017 – $921)	17,992	19,491
Prepaid expenses	21,291	22,183
Prepaid and refundable income taxes	6,726	12,296
Other	9,038	12,132
TOTAL CURRENT ASSETS	631,574	522,349
PROPERTY, PLANT AND EQUIPMENT
Land and structures	338,046	344,224
Revenue equipment	857,846	793,523
Service, office, and other equipment	192,241	179,950
Software	133,816	129,589
Leasehold improvements	9,177	8,888
TOTAL PROPERTY, PLANT AND EQUIPMENT, GROSS	1,531,126	1,456,174
Less allowances for depreciation and amortization	904,180	865,010
PROPERTY, PLANT AND EQUIPMENT, net	626,946	591,164
GOODWILL	108,320	108,320
INTANGIBLE ASSETS, net	70,075	73,469
DEFERRED INCOME TAXES	5,967	5,965
OTHER LONG-TERM ASSETS	74,800	64,374
TOTAL ASSETS	1,517,682	1,365,641
CURRENT LIABILITIES
Accounts payable	154,484	129,099
Income taxes payable	138	324
Accrued expenses	233,076	210,484
Current portion of long-term debt	54,556	61,930
Current portion of pension and postretirement liabilities	12,640	753
TOTAL CURRENT LIABILITIES	454,894	402,590
LONG-TERM DEBT, less current portion	235,970	206,989
PENSION AND POSTRETIREMENT LIABILITIES, less current portion	27,614	39,827
OTHER LONG-TERM LIABILITIES	40,372	15,616
DEFERRED INCOME TAXES	53,741	49,157
STOCKHOLDERS' EQUITY
Common stock, $0.01 par value, authorized 70,000,000 shares; issued 2018: 28,547,578 shares; 2017: 28,495,628 shares	285	285
Additional paid-in capital	325,533	319,436
Retained earnings	488,158	438,379
Treasury stock, at cost, 2018: 2,857,460 shares; 2017: 2,851,578 shares	(86,265)	(86,064)
Accumulated other comprehensive loss	(22,620)	(20,574)
TOTAL STOCKHOLDERS' EQUITY	705,091	651,462
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 1,517,682	$ 1,365,641