CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
CURRENT ASSETS
Cash and cash equivalents	$ 181,731	$ 190,186
Short-term investments	117,657	106,806
Accounts receivable, less allowances (2019 - $6,238; 2018 - $7,380)	296,090	297,051
Other accounts receivable, less allowances (2019 - $463; 2018 - $806)	17,207	19,146
Prepaid expenses	28,546	25,304
Prepaid and refundable income taxes	5,237	1,726
Other	4,982	9,007
TOTAL CURRENT ASSETS	651,450	649,226
PROPERTY, PLANT AND EQUIPMENT
Land and structures	339,255	339,640
Revenue equipment	888,588	858,251
Service, office, and other equipment	218,131	199,230
Software	143,181	138,517
Leasehold improvements	10,058	9,365
TOTAL PROPERTY, PLANT AND EQUIPMENT, GROSS	1,599,213	1,545,003
Less allowances for depreciation and amortization	947,264	913,815
PROPERTY, PLANT AND EQUIPMENT, net	651,949	631,188
GOODWILL	108,320	108,320
INTANGIBLE ASSETS, net	66,700	68,949
OPERATING RIGHT-OF-USE ASSETS	68,810
DEFERRED INCOME TAXES	6,296	7,468
OTHER LONG-TERM ASSETS	80,402	74,080
TOTAL ASSETS	1,633,927	1,539,231
CURRENT LIABILITIES
Accounts payable	166,829	143,785
Income taxes payable	1,942	1,688
Accrued expenses	228,994	243,111
Current portion of long-term debt	47,205	54,075
Current portion of operating lease liabilities	18,273
Current portion of pension and postretirement liabilities	8,231	8,659
TOTAL CURRENT LIABILITIES	471,474	451,318
LONG-TERM DEBT, less current portion	235,001	237,600
OPERATING LEASE LIABILITIES, less current portion	54,040
PENSION AND POSTRETIREMENT LIABILITIES, less current portion	31,874	31,504
OTHER LONG-TERM LIABILITIES	37,268	44,686
DEFERRED INCOME TAXES	61,111	56,441
STOCKHOLDERS' EQUITY
Common stock, $0.01 par value, authorized 70,000,000 shares; issued 2019: 28,786,473 shares, 2018: 28,684,779 shares	288	287
Additional paid-in capital	329,388	325,712
Retained earnings	526,551	501,389
Treasury stock, at cost, 2019: 3,266,169 shares; 2018: 3,097,634 shares	(100,639)	(95,468)
Accumulated other comprehensive loss	(12,429)	(14,238)
TOTAL STOCKHOLDERS' EQUITY	743,159	717,682
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 1,633,927	$ 1,539,231