HA Sustainable Infrastructure Capital, Inc. Quarterly report pursuant to Section 13 or 15(d)

Securitization of Financial Assets - Additional Information (Details)	9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale [Line Items]
Managed assets	$ 5,700,000,000		$ 5,300,000,000
Securitization credit losses	0	$ 0
Greater than 90 Days Past Due [Member]
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale [Line Items]
Payment from debtors to securitization trust	1,000,000
Asset-backed Securities, Securitized Loans and Receivables [Member]
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale [Line Items]
Managed receivables	$ 3,800,000,000		$ 3,300,000,000
Maximum [Member]
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale [Line Items]
Annual servicing fees	0.20%
Maximum [Member] \| Measurement Input, Discount Rate [Member]
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale [Line Items]
Discount rates to determine fair market value of underlying assets	0.07
Minimum [Member] \| Measurement Input, Discount Rate [Member]
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale [Line Items]
Discount rates to determine fair market value of underlying assets	0.03