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Nonrecourse Debt - Analysis of Nonrecourse Debt by Interest Rate (Detail) (USD $)
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6 Months Ended | 12 Months Ended |
|---|---|---|
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Jun. 30, 2013
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Dec. 31, 2012
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| Long Term Debt Maturity [Line Items] | ||
| Total nonrecourse debt | $ 194,136,167 | $ 195,952,169 |
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Fixed-rate promissory notes, interest rates from 2.06% to 5.00% per annum [Member]
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| Long Term Debt Maturity [Line Items] | ||
| Total nonrecourse debt | 90,294,273 | |
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Fixed-rate promissory notes, interest rates from 2.06% to 5.00% per annum [Member] | Minimum [Member]
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| Long Term Debt Maturity [Line Items] | ||
| Nonrecourse debt, Maturity period | 2014 | |
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Fixed-rate promissory notes, interest rates from 2.06% to 5.00% per annum [Member] | Maximum [Member]
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| Long Term Debt Maturity [Line Items] | ||
| Nonrecourse debt, Maturity period | 2032 | |
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Fixed-rate promissory notes, interest rates from 2.26% to 5.00% per annum [Member]
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| Long Term Debt Maturity [Line Items] | ||
| Total nonrecourse debt | 82,753,303 | |
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Fixed-rate promissory notes, interest rates from 2.26% to 5.00% per annum [Member] | Minimum [Member]
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| Long Term Debt Maturity [Line Items] | ||
| Nonrecourse debt, Maturity period | 2014 | |
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Fixed-rate promissory notes, interest rates from 2.26% to 5.00% per annum [Member] | Maximum [Member]
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| Long Term Debt Maturity [Line Items] | ||
| Nonrecourse debt, Maturity period | 2032 | |
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Fixed-rate promissory notes, interest rates from 5.01% to 6.50% per annum [Member]
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| Long Term Debt Maturity [Line Items] | ||
| Total nonrecourse debt | 78,158,522 | 85,300,600 |
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Fixed-rate promissory notes, interest rates from 5.01% to 6.50% per annum [Member] | Minimum [Member]
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| Long Term Debt Maturity [Line Items] | ||
| Nonrecourse debt, Maturity period | 2013 | 2013 |
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Fixed-rate promissory notes, interest rates from 5.01% to 6.50% per annum [Member] | Maximum [Member]
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| Long Term Debt Maturity [Line Items] | ||
| Nonrecourse debt, Maturity period | 2031 | 2031 |
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Fixed-rate promissory notes, interest rates from 6.51% to 8.00% per annum [Member]
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| Long Term Debt Maturity [Line Items] | ||
| Total nonrecourse debt | $ 25,683,372 | $ 27,898,266 |
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Fixed-rate promissory notes, interest rates from 6.51% to 8.00% per annum [Member] | Minimum [Member]
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| Long Term Debt Maturity [Line Items] | ||
| Nonrecourse debt, Maturity period | 2015 | 2013 |
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Fixed-rate promissory notes, interest rates from 6.51% to 8.00% per annum [Member] | Maximum [Member]
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| Long Term Debt Maturity [Line Items] | ||
| Nonrecourse debt, Maturity period | 2031 | 2031 |