Selected Quarterly Results (Unaudited) - Selected Quarterly Results (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended	12 Months Ended
Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Selected Quarterly Financial Information [Abstract]
Revenue	$ 2,547us-gaap_Revenues	$ 1,822us-gaap_Revenues	$ 13,885us-gaap_Revenues	$ 20,690us-gaap_Revenues	$ 3,973us-gaap_Revenues	$ 2,997us-gaap_Revenues	$ 2,764us-gaap_Revenues	$ 1,622us-gaap_Revenues	$ 38,944us-gaap_Revenues	$ 11,356us-gaap_Revenues	$ 54,542us-gaap_Revenues
Gross profit	(516)us-gaap_GrossProfit	1,359us-gaap_GrossProfit	13,198us-gaap_GrossProfit	19,964us-gaap_GrossProfit	3,599us-gaap_GrossProfit	2,354us-gaap_GrossProfit	2,074us-gaap_GrossProfit	1,247us-gaap_GrossProfit
Income (loss) from operations	(18,353)us-gaap_OperatingIncomeLoss	(19,059)us-gaap_OperatingIncomeLoss	(2,041)us-gaap_OperatingIncomeLoss	713us-gaap_OperatingIncomeLoss	(11,799)us-gaap_OperatingIncomeLoss	(17,083)us-gaap_OperatingIncomeLoss	(13,808)us-gaap_OperatingIncomeLoss	(13,712)us-gaap_OperatingIncomeLoss	(38,740)us-gaap_OperatingIncomeLoss	(56,402)us-gaap_OperatingIncomeLoss	7,061us-gaap_OperatingIncomeLoss
Net loss	$ (17,647)us-gaap_NetIncomeLoss	$ (25,256)us-gaap_NetIncomeLoss	$ (6,671)us-gaap_NetIncomeLoss	$ (4,644)us-gaap_NetIncomeLoss	$ (12,770)us-gaap_NetIncomeLoss	$ (18,486)us-gaap_NetIncomeLoss	$ (13,415)us-gaap_NetIncomeLoss	$ (12,723)us-gaap_NetIncomeLoss	$ (54,218)us-gaap_NetIncomeLoss	$ (57,394)us-gaap_NetIncomeLoss	$ 1,652us-gaap_NetIncomeLoss
Basic loss per share	$ (0.36)us-gaap_EarningsPerShareBasic	$ (0.51)us-gaap_EarningsPerShareBasic	$ (0.14)us-gaap_EarningsPerShareBasic	$ (0.11)us-gaap_EarningsPerShareBasic	$ (0.33)us-gaap_EarningsPerShareBasic	$ (0.49)us-gaap_EarningsPerShareBasic	$ (0.35)us-gaap_EarningsPerShareBasic	$ (0.34)us-gaap_EarningsPerShareBasic	$ (1.12)us-gaap_EarningsPerShareBasic	$ (1.51)us-gaap_EarningsPerShareBasic	$ 0.05us-gaap_EarningsPerShareBasic
Diluted loss per share	$ (0.36)us-gaap_EarningsPerShareDiluted	$ (0.51)us-gaap_EarningsPerShareDiluted	$ (0.14)us-gaap_EarningsPerShareDiluted	$ (0.11)us-gaap_EarningsPerShareDiluted	$ (0.33)us-gaap_EarningsPerShareDiluted	$ (0.49)us-gaap_EarningsPerShareDiluted	$ (0.35)us-gaap_EarningsPerShareDiluted	$ (0.34)us-gaap_EarningsPerShareDiluted	$ (1.12)us-gaap_EarningsPerShareDiluted	$ (1.51)us-gaap_EarningsPerShareDiluted	$ 0.05us-gaap_EarningsPerShareDiluted

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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