Restricted Cash - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Restricted Cash and Cash Equivalents Items [Line Items]
Deposits Assets, Current	$ 30,999	$ 337
Solar Tax Partners 1, LLC [Member] | Guarantee Deposit [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Deposits Assets, Current	30,919
Solar Tax Partners 1, LLC [Member] | Reserve [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Deposits Assets, Current	$ 80
Minimum [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Maturity period of guarantee deposit	1 month
Maximum [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Maturity period of guarantee deposit	6 months