CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
CURRENT ASSETS
Cash and cash equivalents	$ 201,909	$ 190,186
Short-term investments	116,579	106,806
Accounts receivable, less allowances (2019 - $5,448; 2018 - $7,380)	282,579	297,051
Other accounts receivable, less allowances (2019 - $476; 2018 - $806)	18,774	19,146
Prepaid expenses	30,377	25,304
Prepaid and refundable income taxes	9,439	1,726
Other	4,745	9,007
TOTAL CURRENT ASSETS	664,402	649,226
PROPERTY, PLANT AND EQUIPMENT
Land and structures	342,122	339,640
Revenue equipment	896,020	858,251
Service, office, and other equipment	233,354	199,230
Software	151,068	138,517
Leasehold improvements	10,383	9,365
TOTAL PROPERTY, PLANT AND EQUIPMENT, Gross	1,632,947	1,545,003
Less allowances for depreciation and amortization	949,355	913,815
PROPERTY, PLANT AND EQUIPMENT, net	683,592	631,188
GOODWILL	88,320	108,320
INTANGIBLE ASSETS, net	58,832	68,949
OPERATING RIGHT-OF-USE ASSETS	68,470
DEFERRED INCOME TAXES	7,725	7,468
OTHER LONG-TERM ASSETS	79,866	74,080
TOTAL ASSETS	1,651,207	1,539,231
CURRENT LIABILITIES
Accounts payable	134,374	143,785
Income taxes payable	12	1,688
Accrued expenses	228,749	243,111
Current portion of long-term debt	57,305	54,075
Current portion of operating lease liabilities	20,265
Current portion of pension and postretirement liabilities	3,572	8,659
TOTAL CURRENT LIABILITIES	444,277	451,318
LONG-TERM DEBT, less current portion	266,214	237,600
OPERATING LEASE LIABILITIES, less current portion	52,277
PENSION AND POSTRETIREMENT LIABILITIES, less current portion	20,294	31,504
OTHER LONG-TERM LIABILITIES	38,892	44,686
DEFERRED INCOME TAXES	66,210	56,441
STOCKHOLDERS' EQUITY
Common stock, $0.01 par value, authorized 70,000,000 shares; issued 2019: 28,810,902 shares, 2018: 28,684,779 shares	288	287
Additional paid-in capital	333,943	325,712
Retained earnings	533,187	501,389
Treasury stock, at cost, 2019: 3,404,639 shares; 2018: 3,097,634 shares	(104,578)	(95,468)
Accumulated other comprehensive income (loss)	203	(14,238)
TOTAL STOCKHOLDERS' EQUITY	763,043	717,682
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 1,651,207	$ 1,539,231