Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 66,127	$ 31,461
Trade, less allowances of $348 and $382, respectively	83,426	90,712
Other	4,202	11,055
Prepaid expenses and other	21,903	20,938
Total current assets	175,658	154,166
Property and equipment:
Less accumulated depreciation	(275,950)	(263,843)
Net property and equipment	654,173	640,394
Other noncurrent assets	1,805	2,026
Total assets	831,636	796,586
Current liabilities:
Accounts payable	25,702	22,917
Insurance and claims accruals	39,595	31,729
Accrued and other current liabilities	24,497	21,680
Total current liabilities	89,794	76,326
Deferred income taxes	121,098	122,022
Noncurrent operating lease liabilities	411	649
Total liabilities	211,303	198,997
Commitments and contingencies (Note 16)
Stockholders’ equity:
Preferred stock, $.01 par value per share; 2,000,000 shares authorized; no shares issued and outstanding	0	0
Common stock, $.01 par value per share; 192,000,000 shares authorized; 82,705,005 shares at December 31, 2020, and 82,055,199 shares at December 31, 2019, issued and outstanding	827	821
Additional paid-in capital	85,070	79,465
Retained earnings	534,436	517,303
Total stockholders’ equity	620,333	597,589
Total liabilities and stockholders’ equity	831,636	796,586
Revenue Equipment [Member]
Property and equipment:
Property and equipment	787,780	764,419
Land and Building [Member]
Property and equipment:
Property and equipment	90,049	88,414
Office Equipment [Member]
Property and equipment:
Property and equipment	$ 52,294	$ 51,404