Indebtedness - Additional Information (Details) - USD ($)	1 Months Ended			9 Months Ended
	Apr. 30, 2015	Dec. 31, 2014	Dec. 31, 2013	Sep. 30, 2015	Sep. 30, 2014	Jul. 31, 2015
Line Of Credit Facility [Line Items]
Repayments of debt				$ 199,860,000	$ 3,683,000
Loss on early extinguishment of debt				431,000
Loan outstanding balance		$ 239,251,000		468,816,000
Solar energy systems, gross		1,566,667,000		1,944,054,000
Repayment of lease obligations				$ 2,670,000	$ 843,000
Basis point
Line Of Credit Facility [Line Items]
Annual Contractual Interest Rate				3.25%
Subordinated Term Loan
Line Of Credit Facility [Line Items]
Repayments of debt		94,400,000
Bank Line of Credit
Line Of Credit Facility [Line Items]
Line of credit facility, amount outstanding		48,597,000		$ 133,294,000
Bank Line of Credit | Credit Facility Agreements with Syndicate of Banks
Line Of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity		50,000,000
Bank Line of Credit | Credit Facility Agreements with Syndicate of Banks | Letter of Credit Sub-Facility
Line Of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity		1,000,000
Bank Line of Credit | Syndicated Working Capital Facility
Line Of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 205,000,000
Line of credit facility, borrowing capacity at closing date				187,000,000
Line of credit facility, amount outstanding				80,000,000
Repayments of line of credit unpaid balance	49,700,000
Minimum unencumbered liquid assets to be maintained				$ 25,000,000
Bank Line of Credit | Syndicated Working Capital Facility | Minimum
Line Of Credit Facility [Line Items]
Interest coverage ratio				200.00%
Non Bank Term Loans
Line Of Credit Facility [Line Items]
Aggregate amount of debt			$ 119,500,000
Repayments of debt	3,500,000
Loss on early extinguishment of debt	$ 431,000
Syndicated Term Loans | Credit Facility Agreements with Syndicate of Banks
Line Of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity		195,400,000
Debt maturity date				Dec. 31, 2021
Syndicated Term Loans | Credit Facility Agreements with Syndicate of Banks | Senior Term Loan
Line Of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity		$ 158,500,000
Syndicated Term Loans | Credit Facility Agreements with Syndicate of Banks | Senior Term Loan | Basis point
Line Of Credit Facility [Line Items]
Debt instrument, variable rate periodic increase		0.25%
Annual Contractual Interest Rate		2.75%
Syndicated Term Loans | Credit Facility Agreements with Syndicate of Banks | Subordinated Term Loan
Line Of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity		$ 24,000,000
Syndicated Term Loans | Credit Facility Agreements with Syndicate of Banks | Subordinated Term Loan | Minimum
Line Of Credit Facility [Line Items]
Debt prepayment penalty percentage		0.00%
Syndicated Term Loans | Credit Facility Agreements with Syndicate of Banks | Subordinated Term Loan | Minimum | Basis point
Line Of Credit Facility [Line Items]
Annual Contractual Interest Rate		1.00%
Syndicated Term Loans | Credit Facility Agreements with Syndicate of Banks | Subordinated Term Loan | Maximum
Line Of Credit Facility [Line Items]
Debt prepayment penalty percentage		2.00%
Syndicated Term Loans | Credit Facility Agreements with Syndicate of Banks | Subordinated Term Loan | Maximum | Basis point
Line Of Credit Facility [Line Items]
Annual Contractual Interest Rate		5.00%
Syndicated Term Loans | Credit Facility Agreements with Syndicate of Banks | Working Capital Revolver Commitment
Line Of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity		$ 5,000,000
Syndicated Term Loans | Credit Facility Agreements with Syndicate of Banks | Senior Secured Revolving Letter Of Credit Facility
Line Of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity		7,900,000
Bank Term Loans
Line Of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity			38,000,000
Notes Payable
Line Of Credit Facility [Line Items]
Proceeds from issuance of senior secured notes			$ 27,200,000
Notes Payable | Payment in Kind ("PIK")
Line Of Credit Facility [Line Items]
Interest Rate			12.00%
Loan outstanding balance		$ 2,900,000		$ 5,500,000
Solar Asset Backed Securities Class A
Line Of Credit Facility [Line Items]
Aggregate amount of debt						$ 100,000,000
Solar Asset Backed Securities Class B
Line Of Credit Facility [Line Items]
Aggregate amount of debt						11,000,000
Asset Backed Securities
Line Of Credit Facility [Line Items]
Secured Borrowings Assets Carrying Amount						$ 192,200,000
Debt instrument discount rate				0.08%
Solar energy systems, gross				$ 119,700,000
Repayment of lease obligations				88,900,000
Net of fees from proceeds from debt instrument				$ 7,300,000