Subsequent Events	12 Months Ended
Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On February 3, 2019, the Company entered into an Agreement and Plan of Merger (the “Merger Agreement”) with Tesla, Inc., a Delaware corporation (“Tesla”) and Cambria Acquisition Corp., a Delaware corporation and a wholly owned subsidiary of Tesla (“Merger Sub”), which contemplates the acquisition of the Company by Tesla, through Merger Sub. The Merger Agreement contemplates that Tesla would commence an all stock exchange offer for all of the issued and outstanding shares of the Company (the “Offer”), followed by a merger of Merger Sub with and into the Company pursuant to which the Company will survive as a wholly-owned subsidiary of Tesla (the “Merger”). In the Offer, each Company stockholder who elects to participate in the Offer will receive a fractional share of common stock of Tesla (“Tesla Common Stock”) for each share of Company common stock (“Company Common Stock”) exchanged in the Offer. Pursuant to the terms and subject to the conditions of the Merger Agreement, as promptly as practicable (but in no event later than four (4) business days following the date on which Tesla files its Annual Report on Form 10-K for the fiscal year ending December 31, 2018), Tesla will commence the Offer to purchase each issued and outstanding share of Company Common Stock for a fraction of a share of Tesla Common Stock, equal to the quotient obtained by dividing $4.75 by the volume weighted average closing sale price of one (1) share of Tesla Common Stock as reported on the NASDAQ Global Select Market (“NASDAQ”) for the five (5) consecutive trading days ending on and including the second trading day immediately preceding the expiration of the Offer (the “Tesla Trading Price”). However, in the event that the Tesla Trading Price is equal to or less than $245.90, then each share of Company Common Stock shall be exchanged for 0.0193 of a share of Tesla Common Stock. Such shares of Tesla Common Stock, plus any cash paid in lieu of any fractional shares of Tesla Common Stock, is referred to as the “Offer Consideration”. At the effective time of the Merger, each outstanding option to purchase Company Common Stock that is outstanding, unexercised and unexpired immediately prior to the effective time shall be automatically assumed by Tesla and converted into and become an option to acquire Tesla Common Stock, as further described in the Merger Agreement, Similarly, each Company restricted share unit that is outstanding immediately prior to the effective time, shall be assumed by Tesla and converted automatically into and become a restricted stock unit covering shares of Tesla Common Stock. The Merger Agreement and the consummation of the transactions contemplated thereby have been unanimously approved by the board of directors of the Company (the “Board”), and the Board has resolved to recommend to the stockholders of the Company to accept the Offer and tender their shares of Company Common Stock to Merger Sub pursuant to the Offer. Under the terms of the Merger Agreement, prior to the expiration of the Offer and subject to customary limitations and conditions, the Company may terminate the Merger Agreement to accept a “superior proposal” if Tesla chooses not to match such proposal, provided that the Company pays Tesla a termination fee of $8.295 million in cash. Each of the parties may also terminate the Merger Agreement if the closing of the Offer has not occurred within five (5) months of the signing of the Merger Agreement.

Subsequent Events

On February 3, 2019, the Company entered into an Agreement and Plan of Merger (the “Merger Agreement”) with Tesla, Inc., a Delaware corporation (“Tesla”) and Cambria Acquisition Corp., a Delaware corporation and a wholly owned subsidiary of Tesla (“Merger Sub”), which contemplates the acquisition of the Company by Tesla, through Merger Sub. The Merger Agreement contemplates that Tesla would commence an all stock exchange offer for all of the issued and outstanding shares of the Company (the “Offer”), followed by a merger of Merger Sub with and into the Company pursuant to which the Company will survive as a wholly-owned subsidiary of Tesla (the “Merger”).

In the Offer, each Company stockholder who elects to participate in the Offer will receive a fractional share of common stock of Tesla (“Tesla Common Stock”) for each share of Company common stock (“Company Common Stock”) exchanged in the Offer. Pursuant to the terms and subject to the conditions of the Merger Agreement, as promptly as practicable (but in no event later than four (4) business days following the date on which Tesla files its Annual Report on Form 10-K for the fiscal year ending December 31, 2018), Tesla will commence the Offer to purchase each issued and outstanding share of Company Common Stock for a fraction of a share of Tesla Common Stock, equal to the quotient obtained by dividing $4.75 by the volume weighted average closing sale price of one (1) share of Tesla Common Stock as reported on the NASDAQ Global Select Market (“NASDAQ”) for the five (5) consecutive trading days ending on and including the second trading day immediately preceding the expiration of the Offer (the “Tesla Trading Price”). However, in the event that the Tesla Trading Price is equal to or less than $245.90, then each share of Company Common Stock shall be exchanged for 0.0193 of a share of Tesla Common Stock. Such shares of Tesla Common Stock, plus any cash paid in lieu of any fractional shares of Tesla Common Stock, is referred to as the “Offer Consideration”.

At the effective time of the Merger, each outstanding option to purchase Company Common Stock that is outstanding, unexercised and unexpired immediately prior to the effective time shall be automatically assumed by Tesla and converted into and become an option to acquire Tesla Common Stock, as further described in the Merger Agreement, Similarly, each Company restricted share unit that is outstanding immediately prior to the effective time, shall be assumed by Tesla and converted automatically into and become a restricted stock unit covering shares of Tesla Common Stock.

The Merger Agreement and the consummation of the transactions contemplated thereby have been unanimously approved by the board of directors of the Company (the “Board”), and the Board has resolved to recommend to the stockholders of the Company to accept the Offer and tender their shares of Company Common Stock to Merger Sub pursuant to the Offer.

Under the terms of the Merger Agreement, prior to the expiration of the Offer and subject to customary limitations and conditions, the Company may terminate the Merger Agreement to accept a “superior proposal” if Tesla chooses not to match such proposal, provided that the Company pays Tesla a termination fee of $8.295 million in cash. Each of the parties may also terminate the Merger Agreement if the closing of the Offer has not occurred within five (5) months of the signing of the Merger Agreement.