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Document And Entity Information - USD ($)
 12 Months Ended
Dec. 31, 2024
Feb. 25, 2025
Jun. 30, 2024
Cover [Abstract]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Dec. 31, 2024    
Document Fiscal Year Focus 2024    
Document Fiscal Period Focus FY    
Entity Registrant Name Byline Bancorp, Inc.    
Entity Central Index Key 0001702750    
Current Fiscal Year End Date --12-31    
Entity Filer Category Large Accelerated Filer    
Entity File Number 001-38139    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 36-3012593    
Entity Address, Address Line One 180 North LaSalle Street    
Entity Address, Address Line Two Suite 300    
Entity Address, City or Town Chicago    
Entity Address, State or Province IL    
Entity Address, Postal Zip Code 60601    
City Area Code 773    
Local Phone Number 244-7000    
Entity Well-known Seasoned Issuer Yes    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Interactive Data Current Yes    
ICFR Auditor Attestation Flag true    
Document Financial Statement Error Correction [Flag] false    
Entity Public Float     $ 734,219,182
Entity Common Stock, Shares Outstanding   44,683,741  
Entity Shell Company false    
Entity Small Business false    
Entity Emerging Growth Company false    
Document Annual Report true    
Document Transition Report false    
Documents Incorporated by Reference Portions of the Registrant’s Definitive Proxy Statement relating to its 2025 Annual Meeting of Stockholders, scheduled to be held on June 3, 2025, are incorporated by reference into Part III of this Report.    
Title of each class Common Stock    
Trading Symbol BY    
Name of each exchange on which registered NYSE    
Auditor Firm ID 659    
Auditor Name Moss Adams LLP    
Auditor Location Portland, Oregon, United States of America    
Auditor Opinion [Text Block]

Opinions on the Financial Statements and Internal Control over Financial Reporting

We have audited the accompanying consolidated statements of financial condition of Byline Bancorp, Inc. and Subsidiaries (the “Company”) as of December 31, 2024 and 2023, the related consolidated statements of operations, comprehensive income (loss), changes in stockholders’ equity, and cash flows for each of the three years in the period ended December 31, 2024, and the related notes (collectively referred to as the “consolidated financial statements”). We also have audited the Company’s internal control over financial reporting as of December 31, 2024, based on criteria established in Internal Control - Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO).

In our opinion, the consolidated financial statements referred to above present fairly, in all material respects, the consolidated financial position of the Company as of December 31, 2024 and 2023, and the consolidated results of its operations and its cash flows for each of the three years in the period ended December 31, 2024, in conformity with accounting principles generally accepted in the United States of America. Also in our opinion, the Company maintained, in all material respects, effective internal control over financial reporting as of December 31, 2024, based on criteria established in Internal Control - Integrated Framework (2013) issued by COSO.