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Note 2 - Summary of Significant Accounting Policies (Details Textual) | 3 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | ---
Dec. 31, 2017 USD ($) | Dec. 31, 2017 USD ($) shares | Dec. 31, 2016 USD ($) shares | Dec. 31, 2015 USD ($) shares | Dec. 31, 2018 USD ($) | Mar. 31, 2015 USD ($)
Investments | $ 0 | $ 0 | $ 0 |  |  |
Book Overdrafts | 0 | 0 | 0 |  |  |
Workers' Compensation Liability | 3,700,000 | 3,700,000 | 3,400,000 |  |  |
Workers' Compensation Liability, Current | 422,000 | $ 422,000 | $ 569,000 |  |  |
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount | shares |  | 196,000 | 198,000 | 179,000 |  |
Number of Customers with Receivable Balance in Excess of Ten Percent of Receivables |  | 2 | 2 |  |  |
Income Tax Expense (Benefit) |  | $ (1,100,000) | $ (4,098,000) | $ (8,523,000) |  |
Accounting Standards Update 2016-09 [Member] |  |  |  |  |  |
Income Tax Expense (Benefit) |  | $ 800,000 |  |  |  |
Accounting Standards Update 2014-09 [Member] | Retained Earnings [Member] | Scenario, Forecast [Member] |  |  |  |  |  |
Cumulative Effect of New Accounting Principle in Period of Adoption |  |  |  |  | $ 1,000,000 |
Sales Revenue, Net [Member] | Customer Concentration Risk [Member] |  |  |  |  |  |
Number of Major Customers |  | 0 | 1 | 2 |  |
Sales Revenue, Net [Member] | Customer Concentration Risk [Member] | Customer One [Member] |  |  |  |  |  |
Concentration Risk, Percentage |  |  | 28.00% | 16.00% |  |
Sales Revenue, Net [Member] | Customer Concentration Risk [Member] | Customer Two [Member] |  |  |  |  |  |
Concentration Risk, Percentage |  |  |  | 13.00% |  |
Accrued Liability [Member] |  |  |  |  |  |
Workers' Compensation Liability, Current | 400,000 | $ 400,000 | $ 600,000 |  |  |
Other Long-term Liabilities [Member] |  |  |  |  |  |
Workers' Compensation Liability, Noncurrent | 3,300,000 | 3,300,000 | 2,800,000 |  |  |
Cost of Sales [Member] |  |  |  |  |  |
Workers Compensation Expense | $ 1,200,000 |  |  |  |  |
Cost of Sales [Member] | Accounting Standards Update 2017-07 [Member] | Year Ended December 31, 2016 [Member] |  |  |  |  |  |
Prior Period Reclassification Adjustment |  | $ 0 | $ 400,000 |  |  |
Water Transmission Group [Member] |  |  |  |  |  |
Goodwill |  |  |  |  |  | $ 5,300,000
Minimum [Member] |  |  |  |  |  |
Finite-Lived Intangible Asset, Useful Life |  | 4 years |  |  |  |
Maximum [Member] |  |  |  |  |  |
Finite-Lived Intangible Asset, Useful Life |  | 15 years |  |  |  |
Land Improvements [Member] | Minimum [Member] |  |  |  |  |  |
Property, Plant and Equipment, Useful Life |  | 15 years |  |  |  |
Land Improvements [Member] | Maximum [Member] |  |  |  |  |  |
Property, Plant and Equipment, Useful Life |  | 30 years |  |  |  |
Building [Member] | Minimum [Member] |  |  |  |  |  |
Property, Plant and Equipment, Useful Life |  | 20 years |  |  |  |
Building [Member] | Maximum [Member] |  |  |  |  |  |
Property, Plant and Equipment, Useful Life |  | 40 years |  |  |  |
Machinery and Equipment [Member] | Minimum [Member] |  |  |  |  |  |
Property, Plant and Equipment, Useful Life |  | 3 years |  |  |  |
Machinery and Equipment [Member] | Maximum [Member] |  |  |  |  |  |
Property, Plant and Equipment, Useful Life |  | 30 years |  |  |  |

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