Basis of Presentation (Policies)	6 Months Ended
Jun. 30, 2013
Basis Of Presentation Disclosure [Abstract]
Warrant accounting	Warrant accounting We account for common stock warrants in accordance with applicable accounting guidance provided in Accounting Standards Codification (ASC) 815, Derivatives and Hedging – Contracts in Entity’s Own Equity, as either derivative liabilities or as equity instruments depending on the specific terms of the warrant agreement. In compliance with applicable securities law, registered common stock warrants that require the issuance of registered shares upon exercise and do not sufficiently preclude an implied right to cash settlement are accounted for as derivative liabilities. We classify these derivative warrant liabilities on the condensed consolidated balance sheets as a long term liability, which is revalued at each balance sheet date subsequent to the initial issuance. We use the Black-Scholes pricing model to value the derivative warrant liability. The Black-Scholes pricing model, which is based, in part, upon unobservable inputs for which there is little or no market data, requires the Company to develop its own assumptions. The Company used the following assumptions for its common stock warrants issued on May 31, 2011. The risk-free interest rate for May 31, 2011 (issuance date), December 31, 2012, and June 30, 2013 were 0.75%, 0.31% and 0.46%, respectively. The volatility of the market price of the Company’s common stock for May 31, 2011, December 31, 2012 and June 30, 2013 were 94.4%, 73.5%, and 108.5%, respectively. The expected average term of the warrant used for all periods was 2.5 years. The Company used the following assumptions for its common stock warrants issued on February 20, 2013. The risk-free interest rate for February 20, 2013 (issuance date) and June 30, 2013 were 0.85% and 1.20%, respectively. The volatility of the market price of the Company’s common stock for February 20, 2013 and June 30, 2013 were 102.0% and 101.8%, respectively. The expected average term of the warrant used for February 20, 2013 and June 30, 2013 were 5.0 years and 4.6 years, respectively. There was no expected dividend yield for the warrants granted. As a result, if factors change and different assumptions are used, the warrant liability and the change in estimated fair value could be materially different. Generally, as the market price of our common stock increases, the fair value of the warrant increases, and conversely, as the market price of our common stock decreases, the fair value of the warrant decreases. Also, a significant increase in the volatility of the market price of the Company's common stock, in isolation, would result in a significantly higher fair value measurement; and a significant decrease in volatility would result in a significantly lower fair value measurement. Changes in the fair value of the warrants are reflected in the condensed consolidated statement of operations as change in fair value of common stock warrant liability.
Joint Venture	Joint Venture We account for investments in joint ventures in which we have significant influence in accordance with applicable accounting guidance in Subtopic 323-10, Investments – Equity Method and Joint Ventures – Overall. On February 29, 2012 we completed the formation of our joint venture with Axane, S.A., a subsidiary of Air Liquide, under the name HyPulsion (the JV). The principal purpose of the JV is to develop and sell hydrogen fuel cell systems for the European material handling market. Axane contributed cash at the closing and will make additional fixed cash contributions in 2013 and 2014 in exchange for an initial 55% ownership of the JV, subject to certain conditions. We have not contributed any cash to the JV and we are not obligated to contribute any cash. We contributed to the JV the right to use our technology, including design and technology know-how on GenDrive systems, in exchange for an initial 45% ownership of the JV. On April 19, 2013 Axane purchased an additional 25% ownership interest in HyPulsion from the Company for a cash purchase price of $3.3 million (Euro 2.5 million). We now own 20% and Axane owns 80% of HyPulsion, and we will share in 20% of the profits from the JV. The Company has the right to purchase an additional 60% of HyPulsion from Axane at any time between January 4, 2018 and January 29, 2018 at a formula price. If the Company exercises its purchase right, Axane will have the right, at any time between February 1, 2018 and December 31, 2021, to require the Company to buy the remaining 20% interest at a formula price. In addition, the Company and HyPulsion also entered into an engineering service agreement under which, among other things, the Company will provide HyPulsion with engineering and technical services for a new fuel cell assembly line and manufacturing execution system. Under the service agreement, HyPulsion has paid the Company approximately $659,000 (Euro 500,000) in the aggregate for services to be performed by the Company. In accordance with the equity method of accounting, the Company will increase its investment in the JV by its share of any earnings, and decrease its investment in the JV by its share of any losses. Losses in excess of the investment must be restored from future profits before we can recognize our proportionate share of profits. As of June 30, 2013, the Company had a zero basis for its investment in the JV.
Redeemable Preferred Stock	Redeemable Preferred Stock On May 8, 2013, the Company entered into a Securities Purchase Agreement with Air Liquide, pursuant to which the Company agreed to issue and sell 10,431 shares of the Company’s Series C Redeemable Convertible Preferred Stock, par value $0.01 per share, for an aggregate purchase price of approximately $2.6 million (Euro 2 million) in cash, as more fully discussed in Note 11, Redeemable Preferred Stock. We account for preferred stock as temporary equity in accordance with applicable accounting guidance in Accounting Standards Codification (ASC) 480, Distinguishing Liabilities from Equity. Dividends on the redeemable preferred stock are accounted for as a reduction in the net income (loss) attributable to common shareholders. In connection with the Air Liquide Investment, as outlined under Joint Venture and Redeemable Preferred Stock above, the Company considered the relative fair value of the components involved in its allocation of the overall investment and the associated accounting.
Recent Accounting Pronouncements	*Recent Accounting Pronouncements:* There are no recently issued accounting standards with pending adoptions that the Company’s management currently anticipates will have any material impact upon its financial statements.

Basis of Presentation (Policies)

6 Months Ended

Jun. 30, 2013

Basis Of Presentation Disclosure [Abstract]

We account for common stock warrants in accordance with applicable accounting guidance provided in Accounting Standards Codification (ASC) 815, Derivatives and Hedging – Contracts in Entity’s Own Equity, as either derivative liabilities or as equity instruments depending on the specific terms of the warrant agreement. In compliance with applicable securities law, registered common stock warrants that require the issuance of registered shares upon exercise and do not sufficiently preclude an implied right to cash settlement are accounted for as derivative liabilities. We classify these derivative warrant liabilities on the condensed consolidated balance sheets as a long term liability, which is revalued at each balance sheet date subsequent to the initial issuance. We use the Black-Scholes pricing model to value the derivative warrant liability. The Black-Scholes pricing model, which is based, in part, upon unobservable inputs for which there is little or no market data, requires the Company to develop its own assumptions.

The Company used the following assumptions for its common stock warrants issued on May 31, 2011. The risk-free interest rate for May 31, 2011 (issuance date), December 31, 2012, and June 30, 2013 were 0.75%, 0.31% and 0.46%, respectively. The volatility of the market price of the Company’s common stock for May 31, 2011, December 31, 2012 and June 30, 2013 were 94.4%, 73.5%, and 108.5%, respectively. The expected average term of the warrant used for all periods was 2.5 years.

The Company used the following assumptions for its common stock warrants issued on February 20, 2013. The risk-free interest rate for February 20, 2013 (issuance date) and June 30, 2013 were 0.85% and 1.20%, respectively. The volatility of the market price of the Company’s common stock for February 20, 2013 and June 30, 2013 were 102.0% and 101.8%, respectively. The expected average term of the warrant used for February 20, 2013 and June 30, 2013 were 5.0 years and 4.6 years, respectively.

There was no expected dividend yield for the warrants granted. As a result, if factors change and different assumptions are used, the warrant liability and the change in estimated fair value could be materially different. Generally, as the market price of our common stock increases, the fair value of the warrant increases, and conversely, as the market price of our common stock decreases, the fair value of the warrant decreases. Also, a significant increase in the volatility of the market price of the Company's common stock, in isolation, would result in a significantly higher fair value measurement; and a significant decrease in volatility would result in a significantly lower fair value measurement. Changes in the fair value of the warrants are reflected in the condensed consolidated statement of operations as change in fair value of common stock warrant liability.

Joint Venture

We account for investments in joint ventures in which we have significant influence in accordance with applicable accounting guidance in Subtopic 323-10, Investments – Equity Method and Joint Ventures – Overall. On February 29, 2012 we completed the formation of our joint venture with Axane, S.A., a subsidiary of Air Liquide, under the name HyPulsion (the JV). The principal purpose of the JV is to develop and sell hydrogen fuel cell systems for the European material handling market. Axane contributed cash at the closing and will make additional fixed cash contributions in 2013 and 2014 in exchange for an initial 55% ownership of the JV, subject to certain conditions. We have not contributed any cash to the JV and we are not obligated to contribute any cash. We contributed to the JV the right to use our technology, including design and technology know-how on GenDrive systems, in exchange for an initial 45% ownership of the JV.

On April 19, 2013 Axane purchased an additional 25% ownership interest in HyPulsion from the Company for a cash purchase price of $3.3 million (Euro 2.5 million). We now own 20% and Axane owns 80% of HyPulsion, and we will share in 20% of the profits from the JV. The Company has the right to purchase an additional 60% of HyPulsion from Axane at any time between January 4, 2018 and January 29, 2018 at a formula price. If the Company exercises its purchase right, Axane will have the right, at any time between February 1, 2018 and December 31, 2021, to require the Company to buy the remaining 20% interest at a formula price.

In addition, the Company and HyPulsion also entered into an engineering service agreement under which, among other things, the Company will provide HyPulsion with engineering and technical services for a new fuel cell assembly line and manufacturing execution system. Under the service agreement, HyPulsion has paid the Company approximately $659,000 (Euro 500,000) in the aggregate for services to be performed by the Company.

In accordance with the equity method of accounting, the Company will increase its investment in the JV by its share of any earnings, and decrease its investment in the JV by its share of any losses. Losses in excess of the investment must be restored from future profits before we can recognize our proportionate share of profits. As of June 30, 2013, the Company had a zero basis for its investment in the JV.

Redeemable Preferred Stock

On May 8, 2013, the Company entered into a Securities Purchase Agreement with Air Liquide, pursuant to which the Company agreed to issue and sell 10,431 shares of the Company’s Series C Redeemable Convertible Preferred Stock, par value $0.01 per share, for an aggregate purchase price of approximately $2.6 million (Euro 2 million) in cash, as more fully discussed in Note 11, Redeemable Preferred Stock. We account for preferred stock as temporary equity in accordance with applicable accounting guidance in Accounting Standards Codification (ASC) 480, Distinguishing Liabilities from Equity. Dividends on the redeemable preferred stock are accounted for as a reduction in the net income (loss) attributable to common shareholders.

In connection with the Air Liquide Investment, as outlined under Joint Venture and Redeemable Preferred Stock above, the Company considered the relative fair value of the components involved in its allocation of the overall investment and the associated accounting.

Recent Accounting Pronouncements

Recent Accounting Pronouncements:

There are no recently issued accounting standards with pending adoptions that the Company’s management currently anticipates will have any material impact upon its financial statements.