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Commitments and Contingent Liabilities (Narrative) (Details) $ in Thousands | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Mar. 31, 2018 USD ($) tie | Mar. 31, 2014 | Dec. 31, 2015 | Dec. 31, 2014 USD ($) tie | Dec. 31, 2013 tie | Dec. 31, 2012 USD ($) | Dec. 31, 2017 USD ($)
Product Liability Contingency |  |  |  |  |  |  |
Accrued warranty | $ 8,706 |  |  |  |  |  | $ 8,682
Number of concrete ties manufactured | tie | 3,000,000 |  |  |  |  |  |
Warranty period |  |  | 10 years |  |  |  |
Accrual for environmental loss | $ 6,134 |  |  |  |  |  | 6,144
Reserve for Concrete Ties |  |  |  |  |  |  |
Product Liability Contingency |  |  |  |  |  |  |
Accrued warranty | $ 7,630 |  |  |  |  |  | $ 7,595
Warranty period |  |  |  |  |  | 5 years |
2005 Contract |  |  |  |  |  |  |
Product Liability Contingency |  |  |  |  |  |  |
Number of concrete ties manufactured ratio | tie | 1.5 |  |  |  |  |  |
Period in which concrete ties will be replaced after sale | 5 years |  |  |  |  |  |
Warranty Policy |  |  |  |  |  |  |
Product Liability Contingency |  |  |  |  |  |  |
Warranty period |  |  |  |  |  | 15 years |
Warranty ratio |  |  |  |  |  | 1 |
The UPRR |  |  |  |  |  |  |
Product Liability Contingency |  |  |  |  |  |  |
Number of concrete ties manufactured | tie | 1,600,000 |  |  |  |  |  |
Warranty period |  |  |  |  |  | 5 years |
Warranty ratio |  |  |  |  |  | 1.5 |
The UPRR | Reserve for Concrete Ties |  |  |  |  |  |  |
Product Liability Contingency |  |  |  |  |  |  |
Litigation settlement amount |  |  |  |  |  | $ 12,000 |
Product warranty expense |  |  |  |  |  | $ 22,000 |
Cure period to claim |  | 90 days |  |  | 90 days |  |
Change in standard product warranty accrual |  |  |  | $ 8,766 |  |  |
Number of unreconciled warranty ties | tie |  |  |  | 90,100 |  |  |
The UPRR | Warranty Policy |  |  |  |  |  |  |
Product Liability Contingency |  |  |  |  |  |  |
Number of ties manufactured that did not meet criteria to be covered as warranty replacement ties | tie |  |  |  |  | 170,000 |  |

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