CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
CURRENT ASSETS
Cash and cash equivalents	$ 82,253	$ 114,280
Short-term investments	56,984	56,838
Restricted cash	962	962
Accounts receivable, less allowances (2017 – $5,283; 2016 – $5,437)	258,931	260,643
Other accounts receivable, less allowances (2017 – $875; 2016 – $849)	18,687	22,041
Prepaid expenses	27,012	22,124
Prepaid and refundable income taxes	11,008	9,909
Other	8,226	4,300
TOTAL CURRENT ASSETS	464,063	491,097
PROPERTY, PLANT AND EQUIPMENT
Land and structures	330,909	324,086
Revenue equipment	742,394	743,860
Service, office, and other equipment	155,618	154,119
Software	123,857	120,877
Leasehold improvements	8,993	8,758
TOTAL PROPERTY, PLANT AND EQUIPMENT, GROSS	1,361,771	1,351,700
Less allowances for depreciation and amortization	838,147	819,174
PROPERTY, PLANT AND EQUIPMENT, net	523,624	532,526
GOODWILL	108,981	108,875
INTANGIBLE ASSETS, net	79,371	80,507
DEFERRED INCOME TAXES	3,064	2,978
OTHER LONG-TERM ASSETS	65,380	66,095
TOTAL ASSETS	1,244,483	1,282,078
CURRENT LIABILITIES
Accounts payable	130,750	133,301
Accrued expenses	190,829	198,731
Current portion of long-term debt	59,995	64,143
TOTAL CURRENT LIABILITIES	381,574	396,175
LONG-TERM DEBT, less current portion	167,075	179,530
PENSION AND POSTRETIREMENT LIABILITIES	37,541	35,848
OTHER LONG-TERM LIABILITIES	15,844	16,790
DEFERRED INCOME TAXES	50,773	54,680
STOCKHOLDERS' EQUITY
Common stock, $0.01 par value, authorized 70,000,000 shares; issued 2017: 28,193,117 shares; 2016: 28,174,424 shares	282	282
Additional paid-in capital	316,802	315,318
Retained earnings	377,444	386,917
Treasury stock, at cost, 2017: 2,565,399 shares	(80,045)	(80,045)
Accumulated other comprehensive loss	(22,807)	(23,417)
TOTAL STOCKHOLDERS' EQUITY	591,676	599,055
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 1,244,483	$ 1,282,078