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

Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Additional Information (Detail)

Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	12 Months Ended			0 Months Ended	1 Months Ended	3 Months Ended	12 Months Ended	0 Months Ended
	Dec. 31, 2014 Segment	Dec. 31, 2013	Dec. 31, 2012	Oct. 20, 2014 State Company	Oct. 31, 2014 State Project	Dec. 31, 2012	Sep. 30, 2012	Oct. 01, 2014
Summary Of Significant Accounting Policies [Line Items]
Financing receivable, past due	90 days
Cash and cash equivalents original maturity period	3 months
Restricted cash and cash equivalents	$ 11,943,000	$ 49,865,000
Impairment loss on goodwill	0us-gaap_GoodwillImpairmentLoss	0us-gaap_GoodwillImpairmentLoss	0us-gaap_GoodwillImpairmentLoss
Real estate investment description	To qualify as a REIT, we must meet a number of organizational and operational requirements, including a requirement that we currently distribute at least 90% of our net taxable income, excluding capital gains, to our shareholders.
Income tax examination, description	We have no examinations in progress, none are expected at this time, and years 2010 through 2013 are open.
Uncertain tax positions	0hasi_UncertainTaxPositions	0hasi_UncertainTaxPositions
Accrued interest and penalties	0	0
Interest and penalties recognized during the year	0	0	0
Number of segment reported	1us-gaap_NumberOfReportableSegments
2013 Plan [Member] \| Performance Based Restricted Stock Award [Member]
Summary Of Significant Accounting Policies [Line Items]
Stock-based award vesting minimum percentage	0.00%
Stock-based award vesting maximum percentage	150.00%
Stock-based award, range of vesting percentage description	The range shares earned is generally between 0% and 150% of the initial target, depending on the extent to which the performance target are met.
Strong Upwind Holdings LLC [Member]
Summary Of Significant Accounting Policies [Line Items]
Project investment amount				144,000,000	144,000,000
Ownership percentage					50.00%
Number of limited liability companies				4
Number of operating projects					10
Number of States				5	5
Strong Upwind Holdings LLC [Member] \| Wind Project Investment [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of limited liability companies					4
Number of operating projects				10
Prior To IPO [Member] \| Federal or State Income Taxes [Member]
Summary Of Significant Accounting Policies [Line Items]
Provision for income taxes						$ 0	$ 0
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Finite-lived intangible asset, useful life	3 years
Percentage of taxable income distributed to stockholders	90.00%
Minimum [Member] \| Strong Upwind Holdings LLC [Member]
Summary Of Significant Accounting Policies [Line Items]
Ownership interest based on voting percentage					4.00%			4.00%
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Finite-lived intangible asset, useful life	15 years
Maximum [Member] \| Strong Upwind Holdings LLC [Member]
Summary Of Significant Accounting Policies [Line Items]
Ownership interest based on voting percentage				17.50%	17.50%