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

Annual report pursuant to Section 13 and 15(d)

Cover
- Document and Entity Information
Financial Statements
Notes to Financial Statements
Accounting Policies
- Summary of Significant Accounting Policies (Policies)
Notes Tables
Notes Details

Fair Value Measurements - Additional Information (Detail)

v2.4.1.9

Fair Value Measurements - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Mar. 31, 2014
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Available-for-sale debt securities at fair value	$ 59.6	$ 59.6	$ 59.6		$ 3.2
Available-for-sale debt securities at cost	56.3	56.3	56.3
Realized gain on sale of investments		3.3	3.3
Financing receivable sold	12.9		12.9
Discount rates to determine fair market value of underlying assets			8.00%us-gaap_FairValueInputsDiscountRate
Change in discount rate	5.00%	5.00%	5.00%	10.00%
Cash deposits held in U.S. banks	70.1	70.1	70.1	81.7
Bank deposits	66.2	66.2	66.2	80.8
Level 3 [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Fair value interest rate spreads, minimum			2.00%
Fair value interest rate spreads, maximum			4.50%
Residual Assets [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Discount rates to determine fair market value of underlying assets			8.00%
Unrealized gain (loss) on residual assets			0.3	0.3
Minimum [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Discount rates based on market observations			7.00%
Minimum [Member] \| Residual Assets [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Discount rates to determine fair market value of underlying assets				8.00%
Maximum [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Discount rates based on market observations			15.00%
Maximum [Member] \| Residual Assets [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Discount rates to determine fair market value of underlying assets				10.00%
Additions			1.0	1.0
Collections			1.0	1.0
Accretion			$ 1.0	$ 1.0

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Adverse Change In Discount Rate For Sensitivity Analysis Of Fair Value Of Interests Continued To Be Held By Transferor Servicing Assets Or Liabilities.

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Amount of debt securities categorized neither as held-to-maturity nor trading.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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