CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
CURRENT ASSETS
Cash and cash equivalents	$ 159,307	$ 120,772
Short-term investments	68,013	56,401
Accounts receivable, less allowances (2018 – $8,057; 2017 – $7,657)	309,112	279,074
Other accounts receivable, less allowances (2018 – $952; 2017 – $921)	19,548	19,491
Prepaid expenses	19,912	22,183
Prepaid and refundable income taxes	4,665	12,296
Other	9,509	12,132
TOTAL CURRENT ASSETS	590,066	522,349
PROPERTY, PLANT AND EQUIPMENT
Land and structures	338,902	344,224
Revenue equipment	818,674	793,523
Service, office, and other equipment	190,109	179,950
Software	131,139	129,589
Leasehold improvements	9,131	8,888
TOTAL PROPERTY, PLANT AND EQUIPMENT, GROSS	1,487,955	1,456,174
Less allowances for depreciation and amortization	896,738	865,010
PROPERTY, PLANT AND EQUIPMENT, net	591,217	591,164
GOODWILL	108,320	108,320
INTANGIBLE ASSETS, net	71,206	73,469
DEFERRED INCOME TAXES	6,226	5,965
OTHER LONG-TERM ASSETS	65,261	64,374
TOTAL ASSETS	1,432,296	1,365,641
CURRENT LIABILITIES
Accounts payable	176,034	129,099
Income taxes payable	511	324
Accrued expenses	221,880	211,237
Current portion of long-term debt	51,562	61,930
TOTAL CURRENT LIABILITIES	449,987	402,590
LONG-TERM DEBT, less current portion	198,070	206,989
PENSION AND POSTRETIREMENT LIABILITIES	36,169	39,827
OTHER LONG-TERM LIABILITIES	38,456	15,616
DEFERRED INCOME TAXES	41,099	49,157
STOCKHOLDERS' EQUITY
Common stock, $0.01 par value, authorized 70,000,000 shares; issued 2018: 28,541,578 shares; 2017: 28,495,628 shares	285	285
Additional paid-in capital	322,895	319,436
Retained earnings	449,442	438,379
Treasury stock, at cost, 2018: 2,857,460 shares; 2017: 2,851,578 shares	(86,265)	(86,064)
Accumulated other comprehensive loss	(17,842)	(20,574)
TOTAL STOCKHOLDERS' EQUITY	668,515	651,462
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 1,432,296	$ 1,365,641