| Quarterly Financial Information [Text Block] |
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Selected Quarterly Financial Data (Unaudited)
| The following tables present unaudited financial data of the Trust for each quarter of 2015 and 2014: Ìý | Ìý |
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| Ìý | $ | 14,721,058 | Ìý | Ìý | $ | 18,186,748 | Ìý | Ìý | $ | 11,795,134 | Ìý | Ìý | $ | 34,739,353 | Ìý | Income before income taxes | Ìý | $ | 13,345,170 | Ìý | Ìý | $ | 17,233,208 | Ìý | Ìý | $ | 10,949,033 | Ìý | Ìý | $ | 33,755,611 | Ìý | |
| Ìý | $ | 8,995,057 | Ìý | Ìý | $ | 11,461,349 | Ìý | Ìý | $ | 7,416,012 | Ìý | Ìý | $ | 22,166,089 | Ìý | Net income per Sub-share Certificate | Ìý | $ | 1.10 | Ìý | Ìý | $ | 1.40 | Ìý | Ìý | $ | 0.90 | Ìý | Ìý | $ | 2.67 | Ìý | Ìý | Ìý |
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| Ìý | $ | 13,295,068 | Ìý | Ìý | $ | 14,756,468 | Ìý | Ìý | $ | 15,583,264 | Ìý | Ìý | $ | 11,581,953 | Ìý | Income before income taxes | Ìý | $ | 12,200,547 | Ìý | Ìý | $ | 13,878,547 | Ìý | Ìý | $ | 14,712,912 | Ìý | Ìý | $ | 10,639,548 | Ìý | |
| Ìý | $ | 8,234,892 | Ìý | Ìý | $ | 9,366,043 | Ìý | Ìý | $ | 9,914,167 | Ìý | Ìý | $ | 7,249,918 | Ìý | Net income per Sub-share Certificate | Ìý | $ | 0.99 | Ìý | Ìý | $ | 1.11 | Ìý | Ìý | $ | 1.17 | Ìý | Ìý | $ | 0.86 | Ìý |
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