Net Loss Per Share - Schedule of Basic and Diluted Net Income (Loss) Per Share (Details) - USD ($) $ in Thousands	4 Months Ended	8 Months Ended	12 Months Ended
	Dec. 31, 2025	Sep. 10, 2025	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Earnings Per Share [Abstract]
Net loss	$ (162)		$ (16,539)	$ (7,187)	$ (8,698)
Less: Net loss attributable to Black Rock OpCo prior to the Transactions		$ (16,377)	(16,377)	0	0
Net income attributable to noncontrolling interest			(102)	20	119
Net loss attributable to Black Rock Coffee Bar, Inc.			$ (60)	$ (7,207)	$ (8,817)