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Comprehensive Income (AOCI Rollforward) (Details) - USD ($) | 12 Months Ended
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Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Roll Forward] |  |  |
Balance at beginning of period | $ (1,130,836) | $ 11,313,015 |
Comprehensive Income | 347,450,807 | 306,026,008 | $ 277,942,231
Balance at end of period | (1,271,305) | (1,130,836) | 11,313,015
Foreign currency translation adjustments |  |  |
Accumulated Other Comprehensive Income (Loss) [Roll Forward] |  |  |
Balance at beginning of period | (44,909) | 1,403,899 | 2,507,922
Other comprehensive income (loss) before reclassifications | (2,818,090) | (1,448,808) | (1,104,023)
Comprehensive Income | (2,818,090) | (1,448,808) | (1,104,023)
Balance at end of period | (2,862,999) | (44,909) | 1,403,899
Unrealized gains(losses) on available-for-sale securities |  |  |
Accumulated Other Comprehensive Income (Loss) [Roll Forward] |  |  |
Balance at beginning of period | 829,907 | 10,868,322 | 19,467,441
Other comprehensive income (loss) before reclassifications | 2,167,196 | (5,513,842) | 1,536,416
Amounts reclassified from accumulated other comprehensive income | (208,128) | (4,524,573) | (10,135,535)
Comprehensive Income | 1,959,068 | (10,038,415) | (8,599,119)
Balance at end of period | 2,788,975 | 829,907 | 10,868,322
Unrealized gains (losses) on derivatives |  |  |
Accumulated Other Comprehensive Income (Loss) [Roll Forward] |  |  |
Balance at beginning of period | (1,915,834) | (959,206) | 0
Other comprehensive income (loss) before reclassifications | (672,419) | (1,659,115) | (959,206)
Amounts reclassified from accumulated other comprehensive income | 1,390,972 | 702,487 | 0
Comprehensive Income | 718,553 | (956,628) | (959,206)
Balance at end of period | $ (1,197,281) | $ (1,915,834) | $ (959,206)

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- Definition Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e637-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e681-108580 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=66004124&loc=SL7669686-108580 + Details
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- Definition Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Other Comprehensive Income -URI http://asc.fasb.org/extlink&oid=51831270 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Comprehensive Income -URI http://asc.fasb.org/extlink&oid=51831223 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e557-108580 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Net Income -URI http://asc.fasb.org/extlink&oid=51831255 + Details
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