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Goodwill and Other Intangible Assets - Additional Information (Detail) (USD $)
 3 Months Ended 12 Months Ended 0 Months Ended
Dec. 31, 2014
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Apr. 30, 2009
Apr. 01, 2009
Dec. 31, 2011
Acquired Finite-Lived Intangible Assets [Line Items]              
Aggregate purchase price           5,135,000stem_BusinessAcquisitionCostOfAcquiredEntityPurchasePriceNet  
Impairment amount of intangible asset 530,000stem_ImpairmentsOfIntangibleAssetFiniteLived 530,000stem_ImpairmentsOfIntangibleAssetFiniteLived         655,000stem_ImpairmentsOfIntangibleAssetFiniteLived
Useful life   11 years 10 months 24 days          
Proceeds from sale of indefinite intangible assets 400,000us-gaap_ProceedsFromSaleOfIntangibleAssets 400,000us-gaap_ProceedsFromSaleOfIntangibleAssets          
Percentage of purchase price allocated to goodwill   42.00%stem_BusinessAcquisitionGoodwillAsPercentageOfPurchasePrice          
Impairment of Goodwill   1,910,062us-gaap_GoodwillImpairmentLoss          
Amortization expense   $ 299,000us-gaap_AmortizationOfIntangibleAssets $ 269,000us-gaap_AmortizationOfIntangibleAssets $ 264,000us-gaap_AmortizationOfIntangibleAssets      
In-process research and development [Member]              
Acquired Finite-Lived Intangible Assets [Line Items]              
Minimum expiration year of intangible assets   2027          
Trade name [Member]              
Acquired Finite-Lived Intangible Assets [Line Items]              
Useful life   15 years     15 years 15 years