XML 13 R1.htm IDEA: XBRL DOCUMENT v3.24.0.1
Document And Entity Information - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2023
Feb. 23, 2024
Jun. 30, 2023
Cover [Abstract]      
Entity Registrant Name ICF INTERNATIONAL, INC.    
Entity Central Index Key 0001362004    
Current Fiscal Year End Date --12-31    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
Entity Shell Company false    
Document Annual Report true    
Document Transition Report false    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Interactive Data Current Yes    
Entity Well-known Seasoned Issuer No    
Entity Common Stock, Shares Outstanding (in shares)   18,715,376  
Entity Public Float     $ 2,309
Document Type 10-K    
Document Period End Date Dec. 31, 2023    
Document Fiscal Year Focus 2023    
Document Fiscal Period Focus FY    
Amendment Flag false    
Entity File Number 001-33045    
Entity Tax Identification Number 22-3661438    
ICFR Auditor Attestation Flag true    
Document Financial Statement Error Correction [Flag] false    
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    
Auditor Firm ID 248    
Auditor Name Grant Thornton LLP    
Auditor Location Arlington, Virginia    
Title of each class Common Stock, $0.001 par value    
Trading Symbol ICFI    
Security Exchange Name NASDAQ    
Documents Incorporated by Reference

List hereunder the following documents if incorporated by reference and the Part of the Form 10-K (e.g., Part I, Part II, etc.) into which the document is incorporated: (1) Any annual report to security holders; (2) Any proxy or information statement; and (3) Any prospectus filed pursuant to Rule 424(b) or (c) under the Securities Act of 1933. The listed documents should be clearly described for identification purposes (e.g., annual report to security holders for fiscal year ended December 24, 1980).

Part III incorporates information by reference from the Proxy Statement for the 2024 Annual Meeting of Stockholders expected to be held in June 2024.