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

Securitization of Receivables - Summary of Certain Transactions with Securitization Trusts (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities [Line Items]
Gains on securitizations	$ 18,136	$ 8,730
Securitization Trust [Member]
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities [Line Items]
Gains on securitizations	15,000	13,000
Purchase of receivables securitized	277,000	394,000
Proceeds from securitizations	292,000	407,000
Cash received from residual and servicing assets	4,000	2,000
Securitization Trust [Member] \| Residual Assets [Member]
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities [Line Items]
Residual and servicing assets included in other assets	$ 35,000	$ 18,000