Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 31,461	$ 56,763
Receivables:
Trade, less allowances of $382 and $348, respectively	90,712	83,033
Other	11,055	3,808
Prepaid expenses and other	20,938	19,924
Total current assets	154,166	163,528
Property and equipment:
Less accumulated depreciation	(263,843)	(228,200)
Net property and equipment	640,394	588,230
Other noncurrent assets	2,026	2,146
Total assets	796,586	753,904
Current liabilities:
Accounts payable	22,917	15,704
Insurance and claims accruals	31,729	28,103
Accrued and other current liabilities	21,680	28,166
Total current liabilities	76,326	71,973
Deferred income taxes	122,022	105,977
Noncurrent operating lease liabilities	649	0
Total liabilities	198,997	177,950
Commitments and contingencies (Note 17)
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; 54,703,466 shares at December 31, 2019, and 54,466,691 shares at December 31, 2018, issued and outstanding	547	545
Additional paid-in capital	79,465	76,814
Retained earnings	517,577	498,595
Total stockholders’ equity	597,589	575,954
Total liabilities and stockholders’ equity	796,586	753,904
Revenue Equipment [Member]
Property and equipment:
Property and equipment	764,419	679,667
Land and Building [Member]
Property and equipment:
Property and equipment	88,414	85,578
Buildings And Land Office Equipment And Other [Member]
Property and equipment:
Property and equipment	$ 51,404	$ 51,185