CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
CURRENT ASSETS
Cash and cash equivalents	$ 164,973	$ 157,042
Short-term investments	61,597	45,909
Restricted cash	1,384	1,386
Accounts receivable, less allowances (2015 – $4,825; 2014 – $5,731)	236,097	228,056
Other accounts receivable, less allowances (2015 – $1,029; 2014 – $1,701)	6,718	6,582
Prepaid expenses	20,801	20,906
Deferred income taxes	38,443	40,220
Prepaid and refundable income taxes	18,134	9,920
Other	3,936	4,968
TOTAL CURRENT ASSETS	552,083	514,989
PROPERTY, PLANT AND EQUIPMENT
Land and structures	273,839	251,836
Revenue equipment	699,844	633,455
Service, office, and other equipment	145,286	136,145
Software	127,010	116,112
Leasehold improvements	25,419	24,377
TOTAL PROPERTY, PLANT AND EQUIPMENT, GROSS	1,271,398	1,161,925
Less allowances for depreciation and amortization	788,351	752,075
PROPERTY, PLANT AND EQUIPMENT, net	483,047	409,850
GOODWILL	96,465	77,078
INTANGIBLE ASSETS, net	76,787	72,809
OTHER ASSETS	54,527	52,896
TOTAL ASSETS	1,262,909	1,127,622
CURRENT LIABILITIES
Accounts payable	130,869	120,325
Income taxes payable	91	527
Accrued expenses	188,727	194,674
Current portion of long-term debt	44,910	25,256
TOTAL CURRENT LIABILITIES	364,597	340,782
LONG-TERM DEBT, less current portion	167,599	102,474
PENSION AND POSTRETIREMENT LIABILITIES	51,241	42,418
OTHER LIABILITIES	12,689	16,667
DEFERRED INCOME TAXES	78,055	64,398
STOCKHOLDERS' EQUITY
Common stock, $0.01 par value, authorized 70,000,000 shares; issued 2015: 27,938,319 shares; 2014: 27,722,010 shares	279	277
Additional paid-in capital	309,653	303,045
Retained earnings	376,827	338,810
Treasury stock, at cost, 2015: 2,080,187 shares; 2014: 1,677,932 shares	(70,535)	(57,770)
Accumulated other comprehensive loss	(27,496)	(23,479)
TOTAL STOCKHOLDERS' EQUITY	588,728	560,883
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 1,262,909	$ 1,127,622