Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities
Net income	$ 8,297,751	$ 12,999,749
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	7,217,901	6,312,164
Amortization of debt issuance costs	23,506	23,418
Deferred income taxes	(3,505,604)	649,077
Loss (gain) on sale of property and equipment	76,810	(17,535)
Other losses (gains)	337	(1,072)
Changes in operating assets and liabilities
Accounts receivable and accrued billings	(2,472,435)	(1,844,340)
Costs and estimated earnings in excess of billings on uncompleted contracts	1,238,753	2,979,100
Residential properties under construction	(860,071)	(1,406,681)
Income taxes receivable	(85,715)	(533,837)
Prepaid expenses and other assets	(130,307)	(43,912)
Land and land development costs	603,603	(2,513,242)
Restricted cash	71,014	134,051
Income taxes payable	0	(483,763)
Accounts payable and accrued liabilities	(1,900,088)	1,221,487
Billings in excess of costs and estimated earnings on uncompleted contracts	(678,789)	610,896
Accrued remediation costs	306,811	(28,309)
Net cash provided by operating activities	8,203,477	18,057,251
Cash flows from investing activities
Proceeds from disposal of property and equipment	133,733	263,876
Proceeds from notes receivable	0	56,048
Purchases of property, buildings and equipment	(10,301,721)	(4,989,663)
Net cash used in investing activities	(10,167,988)	(4,669,739)
Cash flows from financing activities
Proceeds from notes payable	22,600,000	4,700,000
Repayments on notes payable	(22,697,255)	(8,840,137)
Debt issuance costs	(8,125)	(21,965)
Net cash used in financing activities	(105,380)	(4,162,102)
Net (decrease) increase in cash and cash equivalents	(2,069,891)	9,225,410
Cash and cash equivalents at beginning of year	20,599,648	11,374,238
Cash and cash equivalents at end of year	18,529,757	20,599,648
Supplemental disclosure of cash flow information
Interest paid, net of amounts capitalized	621,797	548,959
Income taxes paid, net	4,463,081	8,112,214
Supplemental disclosure of non-cash investing
Liability for equipment acquired	$ 57,279	$ 165,703