v3.26.1

Document And Entity Information - shares	3 Months Ended
Document And Entity Information - shares	Mar. 31, 2026	Apr. 27, 2026
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2026
Document Fiscal Year Focus	2026
Document Fiscal Period Focus	Q1
Trading Symbol	BY
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 Small Business	false
Entity Emerging Growth Company	false
Entity Interactive Data Current	Yes
Document Quarterly Report	true
Document Transition Report	false
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	001-38139
Entity Tax Identification Number	36-3012593
Entity Incorporation, State or Country Code	DE
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 Common Stock, Shares Outstanding		45,409,259
Title of each class	Common Stock
Name of each exchange on which registered	NYSE

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Area code of city

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Cover page.

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End date of current fiscal year in the format --MM-DD.

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Fiscal period values are FY, Q1, Q2, and Q3. 1st, 2nd and 3rd quarter 10-Q or 10-QT statements have value Q1, Q2, and Q3 respectively, with 10-K, 10-KT or other fiscal year statements having FY.

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This is focus fiscal year of the document report in YYYY format. For a 2006 annual report, which may also provide financial information from prior periods, fiscal 2006 should be given as the fiscal year focus. Example: 2006.

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For the EDGAR submission types of Form 8-K: the date of the report, the date of the earliest event reported; for the EDGAR submission types of Form N-1A: the filing date; for all other submission types: the end of the reporting or transition period. The format of the date is YYYY-MM-DD.

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Boolean flag that is true only for a form used as an quarterly report.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Boolean flag that is true only for a form used as a transition report.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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The type of document being provided (such as 10-K, 10-Q, 485BPOS, etc). The document type is limited to the same value as the supporting SEC submission type, or the word 'Other'.

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No definition available.

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Address Line 1 such as Attn, Building Name, Street Name

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Address Line 2 such as Street or Suite number

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Name of the City or Town

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No definition available.

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Code for the postal or zip code

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Name of the state or province.

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No definition available.

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A unique 10-digit SEC-issued value to identify entities that have filed disclosures with the SEC. It is commonly abbreviated as CIK.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Exchange Act
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-Section 12
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Indicate number of shares or other units outstanding of each of registrant's classes of capital or common stock or other ownership interests, if and as stated on cover of related periodic report. Where multiple classes or units exist define each class/interest by adding class of stock items such as Common Class A [Member], Common Class B [Member] or Partnership Interest [Member] onto the Instrument [Domain] of the Entity Listings, Instrument.

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Indicate 'Yes' or 'No' whether registrants (1) have filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that registrants were required to file such reports), and (2) have been subject to such filing requirements for the past 90 days. This information should be based on the registrant's current or most recent filing containing the related disclosure.

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Indicate if registrant meets the emerging growth company criteria.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Commission file number. The field allows up to 17 characters. The prefix may contain 1-3 digits, the sequence number may contain 1-8 digits, the optional suffix may contain 1-4 characters, and the fields are separated with a hyphen.

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No definition available.

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Indicate whether the registrant is one of the following: Large Accelerated Filer, Accelerated Filer, Non-accelerated Filer. Definitions of these categories are stated in Rule 12b-2 of the Exchange Act. This information should be based on the registrant's current or most recent filing containing the related disclosure.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Number 240
-Section 12
-Subsection b-2

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Two-character EDGAR code representing the state or country of incorporation.

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No definition available.

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- Definition

Boolean flag that is true when the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit such files).

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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The exact name of the entity filing the report as specified in its charter, which is required by forms filed with the SEC.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Boolean flag that is true when the registrant is a shell company as defined in Rule 12b-2 of the Exchange Act.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Indicates that the company is a Smaller Reporting Company (SRC).

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Exchange Act
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-Section 12
-Subsection b-2

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The Tax Identification Number (TIN), also known as an Employer Identification Number (EIN), is a unique 9-digit value assigned by the IRS.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Local phone number for entity.

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No definition available.

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Title of a 12(b) registered security.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Exchange Act
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-Section 12
-Subsection b

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Name of the Exchange on which a security is registered.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Trading symbol of an instrument as listed on an exchange.

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BYLINE BANCORP, INC. 10-Q