v3.26.1

Cover - shares	3 Months Ended
Cover - shares	Mar. 31, 2026	Apr. 30, 2026
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2026
Document Transition Report	false
Entity File Number	001-37924
Entity Registrant Name	BlackLine, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-3354276
Entity Address, Address Line One	21300 Victory Boulevard
Entity Address, Address Line Two	12th Floor
Entity Address, City or Town	Woodland Hills
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	91367
City Area Code	818
Local Phone Number	223-9008
Title of 12(b) Security	Common stock, par value $0.01 per share
Trading Symbol	BL
Security Exchange Name	NASDAQ
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		58,660,917
Amendment Flag	false
Document Fiscal Year Focus	2026
Document Fiscal Period Focus	Q1
Entity Central Index Key	0001666134
Current Fiscal Year End Date	--12-31

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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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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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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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Local phone number for entity.

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Title of a 12(b) registered security.

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BLACKLINE, INC. 10-Q