Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income	$ 6,307,000	$ 7,796,000	$ 9,467,000
Adjustments to reconcile net income to cash flows provided by operating activities:
Depreciation	7,994,000	7,344,000	6,906,000
Amortization	315,000	299,000	326,000
Amortization of loan costs	502,000	452,000	476,000
Non-cash lease amortization	409,000	265,000
(Benefit) provision for deferred income taxes	(23,000)	1,308,000	1,062,000
Excess tax benefit from stock-based compensation	16,000	68,000	144,000
Provision for uncollectible accounts receivable	371,000	214,000	553,000
Stock-based compensation	208,000	254,000	308,000
Gain on the sale of property	(211,000)
Changes in operating assets and liabilities
Accounts receivable	(748,000)	(196,000)	(113,000)
Materials and supplies	339,000	(1,152,000)	(102,000)
Prepaid expenses and other assets	811,000	(860,000)	1,982,000
Accounts payable and accrued expenses	755,000	1,000	(37,000)
Advance billings and payments	(137,000)	(73,000)	(203,000)
Other liabilities	(163,000)	(270,000)	(9,000)
Net cash from operating activities	16,745,000	15,450,000	20,760,000
Cash flows used in investing activities:
Acquisition and construction of property and equipment	(10,036,000)	(12,440,000)	(7,983,000)
Proceeds from the sale of property	234,000
Retirement of investment	(3,000)	(4,000)	(11,000)
Net cash used in investing activities	(9,805,000)	(12,444,000)	(7,994,000)
Cash flows used in financing activities:
Loan origination costs	(213,000)	(12,000)	(64,000)
Principal repayment of long-term notes payable	(4,350,000)	(4,350,000)	(11,350,000)
Interest rate cap		4,000	(4,000)
CoBank equity account retirement			119,000
Tax withholdings paid on behalf of employees for restricted stock units	(20,000)	(192,000)	(380,000)
Proceeds from Paycheck Protection Program loan	2,975,000
Net cash used in financing activities	(1,608,000)	(4,550,000)	(11,679,000)
Net increase (decrease) in cash and cash equivalents	5,332,000	(1,544,000)	1,087,000
Cash and cash equivalents, beginning of period	3,113,000	4,657,000	3,570,000
Cash and cash equivalents, end of period	8,445,000	3,113,000	4,657,000
Supplemental disclosures of cash flow information:
Interest paid	3,502,000	4,834,000	5,383,000
Income taxes paid (refunded)	884,000	1,993,000	(502,000)
Issuance of Class A common stock