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Minority Investments - Additional Information (Detail)
 3 Months Ended 9 Months Ended
Oct. 06, 2015
USD ($)
Jun. 30, 2015
USD ($)
Dec. 31, 2015
USD ($)
Item
Dec. 31, 2014
USD ($)
Schedule Of Equity Method Investments [Line Items]        
Impairment of minority interest investment     $ 746,000 $ 3,464,000
Net proceeds from sale of ownership interest     $ 2,155,000 (644,000)
Tres Amigas        
Schedule Of Equity Method Investments [Line Items]        
Number of commonly interconnected power grids | Item     3  
Equity method investment, aggregate cost     $ 5,400,000  
Percentage of ownership interest hold     26.00%  
Impairment of minority interest investment   $ 746,000 $ 746,000  
Net proceeds from sale of ownership interest     (356,000)  
Blade Dynamics Ltd        
Schedule Of Equity Method Investments [Line Items]        
Impairment of minority interest investment       $ 3,500,000
Cost method investment, original cost     $ 8,000,000  
Percentage of outstanding common stock 100.00%      
Net proceeds from sale of ownership interest $ 2,500,000      
Milestone achievement period 3 years      
Blade Dynamics Ltd | Maximum        
Schedule Of Equity Method Investments [Line Items]        
Additional proceeds receivable upon successful achievement of certain milestones $ 1,600,000