CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
CURRENT ASSETS
Cash and cash equivalents	$ 134,788	$ 164,973
Short-term investments	69,608	61,597
Restricted cash	1,385	1,384
Accounts receivable, less allowances (2016 – $4,399; 2015 – $4,825)	226,796	236,097
Other accounts receivable, less allowances (2016 – $1,085; 2015 – $1,029)	6,854	6,718
Prepaid expenses	24,725	20,801
Deferred income taxes	36,510	38,443
Prepaid and refundable income taxes	28,082	18,134
Other	5,012	3,936
TOTAL CURRENT ASSETS	533,760	552,083
PROPERTY, PLANT AND EQUIPMENT
Land and structures	280,510	273,839
Revenue equipment	700,078	699,844
Service, office, and other equipment	148,675	145,286
Software	130,318	127,010
Leasehold improvements	25,645	25,419
TOTAL PROPERTY, PLANT AND EQUIPMENT, GROSS	1,285,226	1,271,398
Less allowances for depreciation and amortization	802,620	788,351
PROPERTY, PLANT AND EQUIPMENT, net	482,606	483,047
GOODWILL	96,577	96,465
INTANGIBLE ASSETS, net	76,300	76,787
OTHER ASSETS	55,988	54,527
TOTAL ASSETS	1,245,231	1,262,909
CURRENT LIABILITIES
Accounts payable	139,607	130,869
Income taxes payable		91
Accrued expenses	176,918	188,727
Current portion of long-term debt	45,905	44,910
TOTAL CURRENT LIABILITIES	362,430	364,597
LONG-TERM DEBT, less current portion	157,485	167,599
PENSION AND POSTRETIREMENT LIABILITIES	56,603	51,241
OTHER LIABILITIES	12,206	12,689
DEFERRED INCOME TAXES	79,256	78,055
STOCKHOLDERS' EQUITY
Common stock, $0.01 par value, authorized 70,000,000 shares; issued 2016: 27,950,867 shares; 2015: 27,938,319 shares	280	279
Additional paid-in capital	311,199	309,653
Retained earnings	368,636	376,827
Treasury stock, at cost, 2016: 2,214,146 shares; 2015: 2,080,187 shares	(73,137)	(70,535)
Accumulated other comprehensive loss	(29,727)	(27,496)
TOTAL STOCKHOLDERS' EQUITY	577,251	588,728
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 1,245,231	$ 1,262,909