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

Annual report pursuant to Section 13 and 15(d)

Income Tax - Additional Information (Detail)

Income Tax - Additional Information (Detail) (USD $)	3 Months Ended						12 Months Ended
Income Tax - Additional Information (Detail) (USD $)	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Sep. 30, 2012
Income Tax Holiday [Line Items]
Income tax (expense) benefit	$ (189,000)us-gaap_IncomeTaxExpenseBenefit	$ (607,000)us-gaap_IncomeTaxExpenseBenefit	$ 830,000us-gaap_IncomeTaxExpenseBenefit	$ (60,000)us-gaap_IncomeTaxExpenseBenefit	$ 251,000us-gaap_IncomeTaxExpenseBenefit		$ (26,000)us-gaap_IncomeTaxExpenseBenefit	$ 251,000us-gaap_IncomeTaxExpenseBenefit
Net deferred tax liabilities	100,000us-gaap_DeferredTaxLiabilities				1,800,000us-gaap_DeferredTaxLiabilities		100,000us-gaap_DeferredTaxLiabilities	1,800,000us-gaap_DeferredTaxLiabilities
Deferred tax assets, operating loss carryforwards, subject to expiration	4,400,000						4,400,000
State net operating loss carryforward expiration period							2034
Federal net operating loss carryforward expiration period							2034
Federal income tax expense (Benefit)						0			0
State and local income tax expense (Benefit)						0			0
Federal Income Tax [Member]
Income Tax Holiday [Line Items]
Dividends payable, date declared	2015-01				2014-01		2015-01	2014-01
Dividend payable, date to be paid							Dec. 19, 2014	Dec. 30, 2013
TRS [Member]
Income Tax Holiday [Line Items]
Deferred tax assets, Valuation allowance	0			2,500,000	0		0	0
Income tax (expense) benefit							0	300,000
Effective income tax rate reconciliation, at federal statutory income tax rate, Percent							35.00%
Effective income tax rate reconciliation, State and local income taxes, Percent							5.00%
Effective tax rate							0.00%
Combined statutory tax rate							40.00%
Release of valuation allowance							2,500,000
Net deferred tax liabilities	100,000				1,800,000		100,000	1,800,000
Federal income tax expense (Benefit)							0	(200,000)
State and local income tax expense (Benefit)								(100,000)
Additional Paid-in Capital [Member] \| TRS [Member]
Income Tax Holiday [Line Items]
Tax impact on additional paid in capital				$ 1,900,000