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Investments (Schedule of Variable Interest Entities) (Details) - LB Pipe & Coupling Products, LLC - USD ($) $ in Thousands | Mar. 31, 2018 | Dec. 31, 2017
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Schedule of Equity Method Investments |  |
Maximum exposure to loss | $ 5,791 | $ 5,845
L B Pipe JV investment |  |
Schedule of Equity Method Investments |  |
Maximum exposure to loss | 3,875 | 3,875
Revolving line of credit |  |
Schedule of Equity Method Investments |  |
Maximum exposure to loss | 1,235 | 1,235
Net investment in direct financing lease |  |
Schedule of Equity Method Investments |  |
Maximum exposure to loss | $ 681 | $ 735

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