CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
CURRENT ASSETS
Cash and cash equivalents	$ 152,236	$ 164,973
Short-term investments	64,081	61,597
Restricted cash	961	1,384
Accounts receivable, less allowances (2016 – $4,789; 2015 – $4,825)	238,775	236,097
Other accounts receivable, less allowances (2016 – $810; 2015 – $1,029)	7,346	6,718
Prepaid expenses	21,558	20,801
Deferred income taxes	37,316	38,443
Prepaid and refundable income taxes	20,386	18,134
Other	5,220	3,936
TOTAL CURRENT ASSETS	547,879	552,083
PROPERTY, PLANT AND EQUIPMENT
Land and structures	287,545	273,839
Revenue equipment	723,312	699,844
Service, office, and other equipment	151,520	145,286
Software	131,328	127,010
Leasehold improvements	25,955	25,419
TOTAL PROPERTY, PLANT AND EQUIPMENT, GROSS	1,319,660	1,271,398
Less allowances for depreciation and amortization	812,287	788,351
PROPERTY, PLANT AND EQUIPMENT, net	507,373	483,047
GOODWILL	96,572	96,465
INTANGIBLE ASSETS, net	75,300	76,787
OTHER ASSETS	56,050	54,527
TOTAL ASSETS	1,283,174	1,262,909
CURRENT LIABILITIES
Accounts payable	145,423	130,869
Income taxes payable		91
Accrued expenses	184,141	188,727
Current portion of long-term debt	55,406	44,910
TOTAL CURRENT LIABILITIES	384,970	364,597
LONG-TERM DEBT, less current portion	170,044	167,599
PENSION AND POSTRETIREMENT LIABILITIES	45,595	51,241
OTHER LIABILITIES	12,301	12,689
DEFERRED INCOME TAXES	87,773	78,055
STOCKHOLDERS' EQUITY
Common stock, $0.01 par value, authorized 70,000,000 shares; issued 2016: 28,113,231 shares; 2015: 27,938,319 shares	281	279
Additional paid-in capital	311,924	309,653
Retained earnings	376,780	376,827
Treasury stock, at cost, 2016: 2,363,533 shares; 2015: 2,080,187 shares	(75,651)	(70,535)
Accumulated other comprehensive loss	(30,843)	(27,496)
TOTAL STOCKHOLDERS' EQUITY	582,491	588,728
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 1,283,174	$ 1,262,909