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

Quarterly report pursuant to Section 13 or 15(d)

Equity - Additional Information (Detail)

Equity - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended
Equity - Additional Information (Detail) (USD $)	Aug. 31, 2014	Mar. 31, 2015	Mar. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Registration of IPO Common Stock, date registered		Aug. 31, 2014
Sale of stock, description of transaction		In August 2014, we filed a registration statement with the SEC registering the resale, from time to time, by certain persons of up to 3,178,410 shares of common stock, comprised of: (1) 1,741,238 shares of common stock issued in connection with our formation transactions at the time of our IPO, (2) 331,282 shares of common stock issuable upon exchange of OP units issued in connection with our formation transactions, which are exchangeable on a one-for-one basis, into cash or, at our option, shares of our common stock and (3) 1,105,890 shares of common stock granted under the 2013 Plan to our directors, officers and other employees.
Proceeds from the sale of the shares	$ 0
Scenario Forecast [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Sale of stock	3,178,410
Shares of common stock issued in connection formation transactions	1,741,238
Shares of common stock granted to directors, officers and other employees	1,105,890
Sale of common stock, value	500,000,000
Scenario Forecast [Member] \| Directors, Officers and Other Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock exchangeable ratio		Exchangeable on a one-for-one basis, into cash or, at our option, shares of our common stock
OP Units [Member] \| Scenario Forecast [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock issuable upon exchange of OP units issued	331,282
Restricted Common Stock [Member] \| 2013 Plan [Member] \| Employees and Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares awarded		174,585
Restricted common shares vesting years		Vest in 2015 to 2019
Restricted Common Stock [Member] \| 2013 Plan [Member] \| Certain Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares awarded		390,131
Restricted Incentive [Member] \| 2013 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity-based compensation expense		2,200,000	500,000
Unrecognized compensation expense		16,400,000
Weighted-average term in which unrecognized compensation expense is expected to be recognized		2 years
Assumed forfeiture rate for calculation of compensation expense		5.00%