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11. Stock-Based Compensation (Details 3) (USD $) | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Dividend-yield | 0.00%us-gaap_FairValueAssumptionsExpectedDividendRate |  |
Minimum |  |  |
Risk-free interest rate | 0.89%us-gaap_FairValueAssumptionsRiskFreeInterestRate / us-gaap_RangeAxis = us-gaap_MinimumMember |  |
Expected volatility | 77.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate / us-gaap_RangeAxis = us-gaap_MinimumMember |  |
Expected life (years) | 2 years 6 months |  |
Maximum |  |  |
Risk-free interest rate | 1.10%us-gaap_FairValueAssumptionsRiskFreeInterestRate / us-gaap_RangeAxis = us-gaap_MaximumMember |  |
Expected volatility | 77.78%us-gaap_FairValueAssumptionsExpectedVolatilityRate / us-gaap_RangeAxis = us-gaap_MaximumMember |  |
Expected life (years) | 3 years |  |
Equity Option [Member] |  |  |
Dividend-yield | 0.00%us-gaap_FairValueAssumptionsExpectedDividendRate / us-gaap_StatementEquityComponentsAxis = us-gaap_StockOptionMember | 0.00%us-gaap_FairValueAssumptionsExpectedDividendRate / us-gaap_StatementEquityComponentsAxis = us-gaap_StockOptionMember | 0.00%us-gaap_FairValueAssumptionsExpectedDividendRate / us-gaap_StatementEquityComponentsAxis = us-gaap_StockOptionMember
Expected volatility |  |  | 79.08%us-gaap_FairValueAssumptionsExpectedVolatilityRate / us-gaap_StatementEquityComponentsAxis = us-gaap_StockOptionMember
Expected life (years) | 3 years | 3 years |
Market value per share on grant date |  |  | $ 5.50 AMTX_MarketValuePerShareOnGrantDate / us-gaap_StatementEquityComponentsAxis = us-gaap_StockOptionMember
Equity Option [Member] | Minimum |  |  |
Risk-free interest rate | 0.74%us-gaap_FairValueAssumptionsRiskFreeInterestRate / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementEquityComponentsAxis = us-gaap_StockOptionMember | 0.42%us-gaap_FairValueAssumptionsRiskFreeInterestRate / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementEquityComponentsAxis = us-gaap_StockOptionMember | 0.28%us-gaap_FairValueAssumptionsRiskFreeInterestRate / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementEquityComponentsAxis = us-gaap_StockOptionMember
Expected volatility | 77.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementEquityComponentsAxis = us-gaap_StockOptionMember | 73.20%us-gaap_FairValueAssumptionsExpectedVolatilityRate / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementEquityComponentsAxis = us-gaap_StockOptionMember |
Expected life (years) |  |  | 2 years
Market value per share on grant date | 4.20 AMTX_MarketValuePerShareOnGrantDate / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementEquityComponentsAxis = us-gaap_StockOptionMember | 4.00 AMTX_MarketValuePerShareOnGrantDate / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementEquityComponentsAxis = us-gaap_StockOptionMember |
Weighted average fair value per share of common stock | 2.14 AMTX_WeightedAverageFairValuePerShareOfCommonStock / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementEquityComponentsAxis = us-gaap_StockOptionMember | 1.92 AMTX_WeightedAverageFairValuePerShareOfCommonStock / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementEquityComponentsAxis = us-gaap_StockOptionMember | $ 2.34 AMTX_WeightedAverageFairValuePerShareOfCommonStock / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementEquityComponentsAxis = us-gaap_StockOptionMember
Equity Option [Member] | Maximum |  |  |
Risk-free interest rate | 1.10%us-gaap_FairValueAssumptionsRiskFreeInterestRate / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementEquityComponentsAxis = us-gaap_StockOptionMember | 0.63%us-gaap_FairValueAssumptionsRiskFreeInterestRate / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementEquityComponentsAxis = us-gaap_StockOptionMember | 0.38%us-gaap_FairValueAssumptionsRiskFreeInterestRate / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementEquityComponentsAxis = us-gaap_StockOptionMember
Expected volatility | 78.43%us-gaap_FairValueAssumptionsExpectedVolatilityRate / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementEquityComponentsAxis = us-gaap_StockOptionMember | 75.55%us-gaap_FairValueAssumptionsExpectedVolatilityRate / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementEquityComponentsAxis = us-gaap_StockOptionMember |
Expected life (years) |  |  | 3 years
Market value per share on grant date | 4.66 AMTX_MarketValuePerShareOnGrantDate / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementEquityComponentsAxis = us-gaap_StockOptionMember | 6.50 AMTX_MarketValuePerShareOnGrantDate / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementEquityComponentsAxis = us-gaap_StockOptionMember |
Weighted average fair value per share of common stock | 2.35 AMTX_WeightedAverageFairValuePerShareOfCommonStock / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementEquityComponentsAxis = us-gaap_StockOptionMember | 3.19 AMTX_WeightedAverageFairValuePerShareOfCommonStock / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementEquityComponentsAxis = us-gaap_StockOptionMember | $ 2.80 AMTX_WeightedAverageFairValuePerShareOfCommonStock / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementEquityComponentsAxis = us-gaap_StockOptionMember

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