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

Annual report pursuant to Section 13 and 15(d)

Our Portfolio - Financing Receivables, Investments, Real Estate and Equity Method Investments - Additional Information (Detail)

Our Portfolio - Financing Receivables, Investments, Real Estate and Equity Method Investments - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2012	Dec. 31, 2014 Investment	Dec. 31, 2014 Investment	Dec. 31, 2013 Investment	Sep. 30, 2012	Mar. 31, 2014	May 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Financing receivables and investments			$ 900,000,000	$ 900,000,000
Deferred funding obligations			88,288,000us-gaap_ContractualObligation	88,288,000us-gaap_ContractualObligation	74,675,000us-gaap_ContractualObligation
Restricted cash			3,000,000hasi_RestrictedCashAndCashEquivalent	3,000,000hasi_RestrictedCashAndCashEquivalent	49,900,000hasi_RestrictedCashAndCashEquivalent
Available-for-sale debt securities at fair value			59,600,000	59,600,000			3,200,000
Investments classified as held-to-maturity carrying value	14,700,000
Sale of investments classified as held-to-maturity	15,500,000
Realized gain on sale of investments classified as held-to-maturity	800,000
Available-for-sale debt securities sold at fair value			59,600,000
Available-for-sale debt securities at cost			56,300,000hasi_AvailableForSaleSecuritiesCost	56,300,000hasi_AvailableForSaleSecuritiesCost
Realized gain on sale of investments			3,300,000	3,300,000
Investments in unrealized loss position			0	0	0
Financing receivable allowance			1,200,000	1,200,000
Charged off of receivable against allowance				9,800,000
Allowance for credit losses			1,200,000	1,200,000	11,000,000	0
Maximum exposure loss for variable interest entity				800,000
Accrued interest income				0us-gaap_InterestExpenseRelatedParty	2,400,000us-gaap_InterestExpenseRelatedParty
Other financing receivables on non accrual status			0	0	0
Provision for credit losses		0hasi_ProvisionForCreditLosses				0hasi_ProvisionForCreditLosses
Loan modifications that qualify as trouble debt restructurings		0		0	0	0
Debt and Real Estate Portfolio [Member]
Financing Receivable, Recorded Investment [Line Items]
% of Debt and Real Estate Portfolio				98.00%
Minimum [Member]
Financing Receivable, Recorded Investment [Line Items]
Lease agreement expected expirations, term				2047
Long term land lease agreements expiration dates range				2033
Long term land lease agreements extended expiration dates range				2052
Maximum [Member]
Financing Receivable, Recorded Investment [Line Items]
Lease agreement expected expirations, term				2061
Long term land lease agreements expiration dates range				2044
Long term land lease agreements extended expiration dates range				2047
November Two Thousand Fourteen [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan expected recovery				800,000
Maximum agreed recovery amount				2,000,000
Energy Source LLC [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable allowance					11,000,000
Financing receivable allowance, face amount								24,000,000
Financial receivable average outstanding balance			$ 11,800,000	$ 11,800,000	$ 24,700,000