CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
CURRENT ASSETS
Cash and cash equivalents	$ 130,395	$ 164,973
Short-term investments	59,346	61,597
Restricted cash	962	1,384
Accounts receivable, less allowances (2016 – $5,118; 2015 – $4,825)	256,316	236,097
Other accounts receivable, less allowances (2016 – $830; 2015 – $1,029)	8,927	6,718
Prepaid expenses	19,622	20,801
Deferred income taxes	39,097	38,443
Prepaid and refundable income taxes	13,934	18,134
Other	4,275	3,936
TOTAL CURRENT ASSETS	532,874	552,083
PROPERTY, PLANT AND EQUIPMENT
Land and structures	296,324	273,839
Revenue equipment	738,350	699,844
Service, office, and other equipment	156,536	145,286
Software	134,312	127,010
Leasehold improvements	27,040	25,419
TOTAL PROPERTY, PLANT AND EQUIPMENT, GROSS	1,352,562	1,271,398
Less allowances for depreciation and amortization	822,623	788,351
PROPERTY, PLANT AND EQUIPMENT, net	529,939	483,047
GOODWILL	110,487	96,465
INTANGIBLE ASSETS, net	82,068	76,787
OTHER LONG-TERM ASSETS	65,500	54,527
TOTAL ASSETS	1,320,868	1,262,909
CURRENT LIABILITIES
Accounts payable	149,971	130,869
Income taxes payable		91
Accrued expenses	187,822	188,727
Current portion of long-term debt	61,251	44,910
TOTAL CURRENT LIABILITIES	399,044	364,597
LONG-TERM DEBT, less current portion	176,363	167,599
PENSION AND POSTRETIREMENT LIABILITIES	42,520	51,241
OTHER LONG-TERM LIABILITIES	15,159	12,689
DEFERRED INCOME TAXES	92,629	78,055
STOCKHOLDERS' EQUITY
Common stock, $0.01 par value, authorized 70,000,000 shares; issued 2016: 28,122,385 shares; 2015: 27,938,319 shares	281	279
Additional paid-in capital	313,794	309,653
Retained earnings	387,646	376,827
Treasury stock, at cost, 2016: 2,499,879 shares; 2015: 2,080,187 shares	(78,129)	(70,535)
Accumulated other comprehensive loss	(28,439)	(27,496)
TOTAL STOCKHOLDERS' EQUITY	595,153	588,728
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 1,320,868	$ 1,262,909