Annual report pursuant to Section 13 and 15(d)

Stock Incentive Plan - Narrative (Details)

v2.4.1.9
Stock Incentive Plan - Narrative (Details) (USD $)
In Thousands, except Share data, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
May 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Common stock, par value (in dollars per share)         $ 0.0001us-gaap_CommonStockParOrStatedValuePerShare  
Granted (in shares) 145,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross 598,360us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross 706,644us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross      
Total intrinsic value of options exercised $ 2,030us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue $ 4,224us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue $ 12,830us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue      
Exercise of stock options (in shares) 482,475us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised 682,619us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised 1,306,145us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised      
Exercised (in usd per share) $ 2.999us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice $ 3.037us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice $ 2.651us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice      
Proceeds from exercises of options 1,447us-gaap_ProceedsFromStockOptionsExercised 2,073us-gaap_ProceedsFromStockOptionsExercised 3,463us-gaap_ProceedsFromStockOptionsExercised      
Weighted average exercise price (in usd per share) $ 7.721us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice $ 7.528us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice $ 6.794us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice $ 5.151us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice    
Stock-based compensation expense 2,493us-gaap_ShareBasedCompensation 2,799us-gaap_ShareBasedCompensation 3,351us-gaap_ShareBasedCompensation      
Stock Options            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Expiration period 10 years          
Options vesting period 5 years          
Share-based compensation vesting percentage 20.00%amrc_ShareBasedCompensationArrangementByShareBasedPaymentAwardVestingPercentage
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember 		         
Ratable vesting percentage 5.00%amrc_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRatableVestingPercentage
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember 		         
Exercise term upon termination 90 days          
Weighted average exercise price (in usd per share) $ 3.97us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember 		$ 3.66us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember 		$ 4.03us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember 		     
Non-vested stock options unrecognized compensation expense $ 3,700us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember 		         
Non-vested stock options unrecognized compensation expense, weighted-average period of recognition 2 years 9 months 18 days          
Class A Common Stock            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Common stock, par value (in dollars per share) $ 0.0001us-gaap_CommonStockParOrStatedValuePerShare
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassAMember 		$ 0.0001us-gaap_CommonStockParOrStatedValuePerShare
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassAMember 		       
Exercise of stock options (in shares) 482,475us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassAMember 		682,619us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassAMember 		1,306,145us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassAMember 		     
2000 Plan            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares reserved for future issuance         28,500,000us-gaap_CommonStockCapitalSharesReservedForFutureIssuance
/ us-gaap_PlanNameAxis
= amrc_StockIncentive2000PlanMember 		 
2010 Plan | Stock Options            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares available for grant (in shares) 8,488,457us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ us-gaap_PlanNameAxis
= amrc_StockIncentive2010PlanMember 		         
2010 Plan | Class A Common Stock            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares reserved for future issuance           10,000,000us-gaap_CommonStockCapitalSharesReservedForFutureIssuance
/ us-gaap_PlanNameAxis
= amrc_StockIncentive2010PlanMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassAMember
Granted (in shares) 1,707,504us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_PlanNameAxis
= amrc_StockIncentive2010PlanMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassAMember