Concentrations of Credit Risk and Major Customers - Revenue (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Concentration Risk [Line Items]
Revenue	$ 16,200	$ 3,613
Sales Revenue, Net [Member]
Concentration Risk [Line Items]
Revenue	13,035	3,185
Sales Revenue, Net [Member] | Zhongwei Hanky Wiye Solar Co., Ltd. [Member]
Concentration Risk [Line Items]
Revenue	8,370
Sales Revenue, Net [Member] | Alxa League Zhiwei Photovoltaic Power Generation Co., Ltd. [Member]
Concentration Risk [Line Items]
Revenue	4,665
Sales Revenue, Net [Member] | KDC Solar Credit LS, LLC [Member]
Concentration Risk [Line Items]
Revenue		$ 3,185
Customer Concentration Risk [Member] | Sales Revenue, Net [Member]
Concentration Risk [Line Items]
Percent of Revenue	81.00%	89.00%
Customer Concentration Risk [Member] | Sales Revenue, Net [Member] | Zhongwei Hanky Wiye Solar Co., Ltd. [Member]
Concentration Risk [Line Items]
Percent of Revenue	52.00%
Customer Concentration Risk [Member] | Sales Revenue, Net [Member] | Alxa League Zhiwei Photovoltaic Power Generation Co., Ltd. [Member]
Concentration Risk [Line Items]
Percent of Revenue	29.00%
Customer Concentration Risk [Member] | Sales Revenue, Net [Member] | KDC Solar Credit LS, LLC [Member]
Concentration Risk [Line Items]
Percent of Revenue		89.00%