Quarterly report pursuant to Section 13 or 15(d)

Cover Page

v3.21.2
Cover Page - shares
 9 Months Ended
Sep. 30, 2021
Nov. 03, 2021
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Sep. 30, 2021  
Document Transition Report false  
Entity File Number 001-35877  
Entity Registrant Name HANNON ARMSTRONG SUSTAINABLE INFRASTRUCTURE CAPITAL, INC.  
Entity Incorporation, State or Country Code MD  
Entity Tax Identification Number 46-1347456  
Entity Address, Address Line One 1906 Towne Centre Blvd  
Entity Address, Address Line Two Suite 370  
Entity Address, City or Town Annapolis,  
Entity Address, State or Province MD  
Entity Address, Postal Zip Code 21401  
City Area Code 410  
Local Phone Number 571-9860  
Title of 12(b) Security Common Stock, $0.01 par value per share  
Trading Symbol HASI  
Security Exchange Name NYSE  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   84,693,740
Amendment Flag false  
Document Fiscal Year Focus 2021  
Document Fiscal Period Focus Q3  
Entity Central Index Key 0001561894  
Current Fiscal Year End Date --12-31