Annual report pursuant to Section 13 and 15(d)

Equity Method Investment and Receivable from Investee - Additional Information (Detail)

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Equity Method Investment and Receivable from Investee - Additional Information (Detail) (USD $)
 12 Months Ended 1 Months Ended 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Dec. 19, 2011
Real Goods Solar
Dec. 31, 2012
Real Goods Solar
Dec. 31, 2011
Real Goods Solar
Dec. 31, 2010
Real Goods Solar
Dec. 31, 2012
Real Goods Solar
Riverside Renewable Energy Investments
Dec. 31, 2011
Real Goods Solar
Class B Common Stock
Vote
Dec. 31, 2012
Real Goods Solar
Class A Common Stock
Dec. 31, 2011
Real Goods Solar
Class A Common Stock
Vote
Nov. 13, 2012
Real Goods Solar
Scenario 1
Dec. 31, 2012
Real Goods Solar
Scenario 2
Subsidiary or Equity Method Investee [Line Items]                          
Number of votes per share                 10   1    
Voting ownership percentage                     37.50%    
Loss from deconsolidation pretax   $ (4,550,000) [1]       $ (4,550,000)              
After tax gain on adjustment to a deferred tax liability           2,600,000              
Loan advanced Real Goods Solar           1,700,000              
Percentage annual interest rate on advanced investment           10.00%              
Maturity date of loan advanced                       Apr. 30, 2013 Apr. 26, 2013
Additional loan to be advanced         1,000,000     1,000,000          
Additional loan to be advanced, end date         Mar. 31, 2013                
Tenant improvements purchase price         200,000                
Noncash portion of net loss (18,410,000) [1]       17,000,000                
Goodwill, net deferred tax assets, and other asset impairment charges         38,100,000                
Valuation allowance for a deferred tax asset         1,600,000                
Interest received on loan         200,000                
Carrying values of equity method investment   14,300,000     0                
Income tax benefit         6,000,000 7,100,000              
Equity investment related transactions non cash loss         12,400,000                
Federal income tax rate 34.00% 34.00% 34.00%   34.00%                
Operating loss carryforwards beginning expiration year         2018                
Portion of net operating loss carryforwards         4,400,000                
Deferred tax asset related to Tax Sharing Agreement 1,600,000       1,600,000                
Lease agreement period       5 years                  
Monthly lease payments       16,300                  
Lease rate per square foot agreed to cancel         3                
Owned Class A common stock             54.60%     37.50%      
Estimated fair value based on the closing market price of Class A common stock                   7,600,000      
Equity in the net assets         $ 1,500,000                
[1] RSOL was deconsolidated and accounted for as an equity method investment effective December 31, 2011. Consequently, RSOL is reported as an equity method investment for the year ended December 31, 2012 and as a consolidated subsidiary for the years ended December 31, 2011 and 2010.