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

Fair Value Measurements - Additional Information (Details) - Level 3	Mar. 31, 2020	Dec. 31, 2019
Measurement Input, Interest Rate \| Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
Investments, measurement input	0.01
Measurement Input, Interest Rate \| Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
Investments, measurement input		0.04
Measurement Input, Discount Rate
Fair Value, Option, Quantitative Disclosures [Line Items]
Investments, measurement input	0.037	0.044
Securitization residual assets \| Measurement Input, Interest Rate \| Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
Investments, measurement input	0.02
Securitization residual assets \| Measurement Input, Interest Rate \| Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
Investments, measurement input		0.07
Securitization residual assets \| Measurement Input, Discount Rate
Fair Value, Option, Quantitative Disclosures [Line Items]
Investments, measurement input	0.042	0.044