CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
CURRENT ASSETS
Cash and cash equivalents	$ 138,399	$ 190,186
Short-term investments	116,225	106,806
Accounts receivable, less allowances (2019 – $6,655; 2018 – $7,380)	294,853	297,051
Other accounts receivable, less allowances (2019 – $456; 2018 – $806)	16,925	19,146
Prepaid expenses	31,064	25,304
Prepaid and refundable income taxes	4,610	1,726
Other	4,466	9,007
TOTAL CURRENT ASSETS	606,542	649,226
PROPERTY, PLANT AND EQUIPMENT
Land and structures	340,764	339,640
Revenue equipment	856,370	858,251
Service, office, and other equipment	206,959	199,230
Software	142,062	138,517
Leasehold improvements	9,766	9,365
TOTAL PROPERTY, PLANT AND EQUIPMENT, GROSS	1,555,921	1,545,003
Less allowances for depreciation and amortization	932,945	913,815
PROPERTY, PLANT AND EQUIPMENT, net	622,976	631,188
GOODWILL	108,320	108,320
INTANGIBLE ASSETS, net	67,820	68,949
OPERATING RIGHT OF USE ASSETS	68,737
DEFERRED INCOME TAXES	6,905	7,468
OTHER LONG-TERM ASSETS	78,357	74,080
TOTAL ASSETS	1,559,657	1,539,231
CURRENT LIABILITIES
Accounts payable	145,590	143,785
Income taxes payable	241	1,688
Accrued expenses	211,533	243,111
Current portion of long-term debt	48,809	54,075
Current portion of operating lease liabilities	17,678
Current portion of pension and postretirement liabilities	7,984	8,659
TOTAL CURRENT LIABILITIES	431,835	451,318
LONG-TERM DEBT, less current portion	227,649	237,600
OPERATING LEASE LIABILITIES, less current portion	54,444
PENSION AND POSTRETIREMENT LIABILITIES, less current portion	31,695	31,504
OTHER LONG-TERM LIABILITIES	36,406	44,686
DEFERRED INCOME TAXES	55,873	56,441
STOCKHOLDERS' EQUITY
Common stock, $0.01 par value, authorized 70,000,000 shares; issued 2019: 28,685,313 shares, 2018: 28,684,779 shares	287	287
Additional paid-in capital	327,762	325,712
Retained earnings	504,225	501,389
Treasury stock, at cost, 2019: 3,172,019 shares; 2018: 3,097,634 shares	(98,131)	(95,468)
Accumulated other comprehensive loss	(12,388)	(14,238)
TOTAL STOCKHOLDERS' EQUITY	721,755	717,682
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 1,559,657	$ 1,539,231