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Summary of Significant Accounting Policies - Goodwill and Intangible Assets (Details) (USD $)
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1 Months Ended | 3 Months Ended | 12 Months Ended | 3 Months Ended | 3 Months Ended | 12 Months Ended | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Apr. 30, 2011
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Sep. 30, 2012
Agreement
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Dec. 31, 2013
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Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2013
ESP
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Dec. 31, 2013
Ennovate
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Sep. 30, 2012
FAME
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Dec. 31, 2012
FAME
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Jul. 31, 2012
FAME
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Sep. 30, 2012
AEG
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Dec. 31, 2012
AEG
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Aug. 31, 2011
AEG
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Dec. 31, 2012
Ameresco Southwest
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Dec. 31, 2011
Ameresco Southwest
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Jul. 31, 2012
AIS
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Dec. 31, 2011
AIS
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Dec. 31, 2013
Minimum
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Dec. 31, 2013
Maximum
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| Goodwill [Line Items] | |||||||||||||||||||
| Impairment of goodwill | $ 0 | $ 1,016,325 | $ 0 | ||||||||||||||||
| Goodwill recorded for acquisitions | 53,074,362 | 48,968,390 | 47,881,346 | 2,631,562 | 1,050,303 | 1,886,945 | 1,886,945 | 8,728,169 | 8,728,169 | 16,545,434 | 16,545,434 | 1,549,467 | 1,549,467 | ||||||
| Percentage of stock acquired | 100.00% | 100.00% | |||||||||||||||||
| Number of purchase agreements | 2 | ||||||||||||||||||
| Intangible assets amortization period | 1 year | 14 years | |||||||||||||||||
| Additional payment | $ 1,956,366 | $ 0 | $ 0 | $ 1,956,366 | |||||||||||||||