CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY (UNAUDITED) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2024		62,813
Beginning balance at Dec. 31, 2024	$ 446,669	$ 628	$ 495,391	$ (361)	$ (48,989)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises (in shares)		52
Stock option exercises	2,133	$ 1	2,132
Vesting of restricted stock units (in shares)		316
Vesting of restricted stock units	3	$ 3
Repurchases of common stock, including excise taxes (in shares)		(920)
Repurchases of common stock, including excise taxes	(45,724)	$ (9)	(45,715)
Acquisition of common stock for tax withholding obligations	(10,939)		(10,939)
Stock-based compensation	19,523		19,523
Other comprehensive income (loss)	183			183
Net income attributable to BlackLine, Inc., including adjustment to redeemable non-controlling interest	6,055		1,178		4,877
Ending balance (in shares) at Mar. 31, 2025		62,261
Ending balance at Mar. 31, 2025	417,903	$ 623	461,570	(178)	(44,112)
Beginning balance (in shares) at Dec. 31, 2025		59,881
Beginning balance at Dec. 31, 2025	332,326	$ 599	356,841	(296)	(24,818)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises (in shares)		3
Stock option exercises	54		54
Stock option exercises - redeemable non-controlling interest	78		78
Vesting of restricted stock units (in shares)		468
Vesting of restricted stock units	$ 5	$ 5
Repurchases of common stock, including excise taxes (in shares)	(1,200)	(1,180)
Repurchases of common stock, including excise taxes	$ (47,403)	$ (12)	(47,391)
Acquisition of common stock for tax withholding obligations	(11,763)		(11,763)
Stock-based compensation	24,859		24,859
Other comprehensive income (loss)	(332)			(332)
Net income attributable to BlackLine, Inc., including adjustment to redeemable non-controlling interest	8,126		4,629		3,497
Ending balance (in shares) at Mar. 31, 2026		59,172
Ending balance at Mar. 31, 2026	$ 305,950	$ 592	$ 327,307	$ (628)	$ (21,321)