Investments - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended		6 Months Ended		1 Months Ended	6 Months Ended			12 Months Ended
	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Oct. 31, 2013 Class A Common Stock	Jun. 30, 2014 Real Goods Solar	Jun. 30, 2013 Real Goods Solar	Jun. 30, 2013 Real Goods Solar Class A Common Stock	Dec. 31, 2013 Real Goods Solar Class A Common Stock
Schedule of Equity Method Investments [Line Items]
Common stock value						$ 1,200,000
Gain from sale of investment	500,000	1,042,000	16,429,000	1,480,000	16,429,000		1,000,000	16,400,000		25,000,000
Common stock, Voting percentage									20.00%
Carrying value of investment							$ 0