Variable Interest Entities (Details)			1 Months Ended		3 Months Ended			9 Months Ended		12 Months Ended
Variable Interest Entities (Details)	Jan. 01, 2025 USD ($)	Nov. 21, 2024 USD ($)	Jul. 31, 2025 USD ($)	Feb. 29, 2016 solar_project	Sep. 30, 2025 USD ($) solar_project tax_equity_partnership	Mar. 31, 2025 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2025 USD ($) solar_project tax_equity_partnership	Sep. 30, 2024 USD ($)	Dec. 31, 2024 USD ($)	Mar. 11, 2025 USD ($)
Variable Interest Entity [Line Items]
Number of tax equity partnerships \| tax_equity_partnership					11			11
Assets					$ 3,414,404,000			$ 3,414,404,000		$ 3,245,045,000
Liabilities					2,158,402,000			2,158,402,000		1,903,976,000
Noncontrolling interests					120,205,000			120,205,000		115,057,000
Less: Distributions paid in the current period								3,573,000	$ 179,000
Contributions from noncontrolling interests, net								37,588,000	87,692,000
Gain on deconsolidation, net					$ 0		$ 0	0	$ (5,722,000)
Number of solar projects \| solar_project					2
Illinois Winds LLC \| GREC II \| Related Party
Variable Interest Entity [Line Items]
Decrease from deconsolidation								116,000,000
Gain on deconsolidation, net								12,700,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Illinois Winds LLC
Variable Interest Entity [Line Items]
Reimbursement of construction costs		$ 35,900,000
Construction loan receivable		$ 40,100,000			$ 1,100,000			1,100,000
Construction loan receivable, amount received					38,900,000			38,900,000
Development fee payable					9,000,000			9,000,000
Disposal group, property, plant, and equipment					117,000,000			117,000,000
Disposal group, asset retirement obligations								1,500,000
Other current assets					$ 500,000			$ 500,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Illinois Winds LLC \| GREC II \| Related Party
Variable Interest Entity [Line Items]
Noncontrolling interests										40,800,000
Contributions from noncontrolling interests, net										26,300,000
Proceeds from noncontrolling interests, construction costs										49,100,000
Aurora
Variable Interest Entity [Line Items]
Number of solar projects \| solar_project				16
Equity method ownership percentage					49.00%			49.00%
OYA
Variable Interest Entity [Line Items]
Number of solar projects \| solar_project								19
Equity method ownership percentage			30.00%		50.00%			50.00%
GDEV OYA Lender
Variable Interest Entity [Line Items]
Equity method ownership percentage			30.00%
GDEV Management Holdings LLC \| Greenbacker Capital Management LLC
Variable Interest Entity [Line Items]
Interest rate	6.00%
GDEV Management Holdings LLC \| Greenbacker Capital Management LLC
Variable Interest Entity [Line Items]
Maximum borrowing capacity	$ 4,000,000.0
GDEV OYA Lender
Variable Interest Entity [Line Items]
Distribution received			$ 3,000,000
LLC agreement, retained initial reserves			2,000,000
LLC agreement, preferred return to preferred investor			1,500,000
GDEV OYA Lender \| GREC
Variable Interest Entity [Line Items]
LLC agreement, preferred return to certain investor			$ 4,700,000
GDEV GP
Variable Interest Entity [Line Items]
Noncontrolling interests					$ 900,000			$ 900,000		0
GDEV I
Variable Interest Entity [Line Items]
Maximum exposure to loss					$ 2,800,000			$ 2,800,000
Payments for advance to affiliate						$ 7,400,000
GDEV I \| GDEV GP
Variable Interest Entity [Line Items]
Ownership percentage held by noncontrolling owners					2.00%			2.00%
GDEV II
Variable Interest Entity [Line Items]
Maximum exposure to loss					$ 3,700,000			$ 3,700,000
GDEV II \| GDEV GP II
Variable Interest Entity [Line Items]
Ownership percentage held by noncontrolling owners					1.96%			1.96%
OYA \| Guarantee of Tax Credit Recapture
Variable Interest Entity [Line Items]
Guarantor obligations											$ 1,500,000
Reporting entity involvement, decrease each year, amount											$ 500,000
GDEV Management Holdings LLC
Variable Interest Entity [Line Items]
Noncontrolling interests					$ 1,800,000			$ 1,800,000		0
GDEV Management Holdings LLC \| Related Party of GCM
Variable Interest Entity [Line Items]
Ownership percentage	25.00%
GDEV Management Holdings LLC \| Greenbacker Capital Management LLC
Variable Interest Entity [Line Items]
Ownership percentage	75.00%
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Assets					1,700,000,000			1,700,000,000		1,800,000,000
Liabilities					272,200,000			272,200,000		$ 288,000,000.0
Variable Interest Entity, Primary Beneficiary \| GDEV Management Holdings LLC \| GDEV Management Holdings LLC
Variable Interest Entity [Line Items]
Assets					700,000			700,000
Liabilities					$ 1,400,000			$ 1,400,000

Greenbacker Renewable Energy Co LLC 10-Q