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Geographic information (Details) (USD $)
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9 Months Ended | 12 Months Ended | |||
|---|---|---|---|---|---|
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Sep. 30, 2013
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Sep. 30, 2012
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Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2010
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| Revenues from External Customers and Long-Lived Assets [Line Items] | |||||
| Revenues - owned units | $ 29,136,159 | $ 44,261,251 | $ 56,429,452 | $ 43,655,381 | $ 38,477,190 |
| Management, incentive and royalty fee revenue | 5,585,556 | 2,417,718 | 3,691,270 | 2,436,280 | 184,483 |
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United States [Member]
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|||||
| Revenues from External Customers and Long-Lived Assets [Line Items] | |||||
| Revenues - owned units | 56,429,452 | ||||
| Management, incentive and royalty fee revenue | 3,496,914 | ||||
| Net assets (liabilities) | 3,031,053 | ||||
|
Foreign [Member]
|
|||||
| Revenues from External Customers and Long-Lived Assets [Line Items] | |||||
| Revenues - owned units | |||||
| Management, incentive and royalty fee revenue | 194,356 | ||||
| Net assets (liabilities) | $ (542,306) | ||||