Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
OPERATING ACTIVITIES:
Net income	$ 16,955,000	$ 8,676,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	26,801,000	24,358,000
Bad debt expense	216,000	389,000
Stock compensation-net of excess tax benefits	526,000	395,000
Provision for deferred income taxes	4,923,000	2,158,000
Recognized (gain) loss on marketable equity securities	(2,593,000)	810,000
Gain on sale or disposition of equipment	(327,000)	(515,000)
Changes in operating assets and liabilities:
Accounts receivable	1,119,000	(17,258,000)
Prepaid expenses, deposits, inventories, and other assets	2,690,000	3,314,000
Income taxes (payable) refundable	(98,000)	124,000
Trade accounts payable	1,385,000	5,361,000
Accrued expenses and other liabilities	1,602,000	1,712,000
Net cash provided by operating activities	53,199,000	29,524,000
INVESTING ACTIVITIES:
Purchases of property and equipment	(26,912,000)	(39,768,000)
Proceeds from disposition of equipment	7,760,000	4,450,000
Sales of marketable equity securities	762,000
Purchases of marketable equity securities, net of return of capital	(72,000)	(2,006,000)
Net cash used in investing activities	(18,462,000)	(37,324,000)
FINANCING ACTIVITIES:
Borrowings under line of credit	283,704,000	299,959,000
Repayments under line of credit	(283,187,000)	(274,702,000)
Borrowings of long-term debt	16,386,000	25,046,000
Repayments of long-term debt	(37,006,000)	(37,002,000)
Borrowings under margin account	252,000	2,166,000
Repayments under margin account	(1,431,000)	(565,000)
Repurchases of common stock	(13,441,000)	(7,531,000)
Exercise of stock options	0	468,000
Net cash (used in) provided by financing activities	(34,723,000)	7,839,000
NET INCREASE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	14,000	39,000
CASH, CASH EQUIVALENTS AND RESTRICTED CASH -Beginning of period	282,000
CASH, CASH EQUIVALENTS AND RESTRICTED CASH -End of period	296,000	263,000
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION-
Interest	4,102,000	2,452,000
Income taxes	292,000	53,000
NONCASH INVESTING AND FINANCING ACTIVITIES-
Purchases of property and equipment included in accounts payable	$ 566,000	$ 9,888,000