v3.25.2
Document And Entity Information - shares
6 Months Ended
Jun. 30, 2025
Jul. 25, 2025
Cover [Abstract]    
Entity Registrant Name ICF International, Inc.  
Entity Central Index Key 0001362004  
Trading Symbol ICFI  
Security Exchange Name NASDAQ  
Current Fiscal Year End Date --12-31  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Common Stock, Shares Outstanding   18,428,490
Document Type 10-Q  
Document Period End Date Jun. 30, 2025  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q2  
Amendment Flag false  
Entity Current Reporting Status Yes  
Entity Shell Company false  
Entity File Number 001-33045  
Entity Tax Identification Number 22-3661438  
Entity Incorporation State Country Code DE  
Entity Address, Address Line One 1902 Reston Metro Plaza  
Entity Address, City or Town Reston  
Entity Address, State or Province VA  
Entity Address, Postal Zip Code 20190  
City Area Code 703  
Local Phone Number 934-3000  
Title of each class Common Stock  
Entity Interactive Data Current Yes  
Document Quarterly Report true  
Document Transition Report false