Organization and Nature of Operations (Details) $ / shares in Units, $ in Millions	Sep. 15, 2025 USD ($) vote $ / shares shares	Mar. 31, 2026 store state
Product Information [Line Items]
Number of stores \| store		190
Number of states \| state		7
Recapitalized ownership (in shares)	43,079,227
Black Rock OpCo \| Affiliate Of Co-Founders \| LLC Units
Product Information [Line Items]
Sale of stock (in shares)	3,118,938
Public offering price (in dollars per share) \| $ / shares	$ 20.00
Net proceeds from IPO \| $	$ 62.4
Black Rock OpCo \| LLC Units held by Black Rock Coffee Bar, Inc. \| LLC Units
Product Information [Line Items]
Sale of stock (in shares)	3,857,642
Net proceeds from IPO \| $	$ 71.8
Continuing Equity Owners \| LLC Units
Product Information [Line Items]
Sale of stock (in shares)	13,054,122
Net proceeds from IPO \| $	$ 242.8
Class A Common stock
Product Information [Line Items]
Number of votes per share \| vote	1
Class B Common stock
Product Information [Line Items]
Number of votes per share \| vote	1
Class C Common stock
Product Information [Line Items]
Number of votes per share \| vote	10
Share ownership threshold	33.00%
IPO
Product Information [Line Items]
Sale of stock (in shares)	16,911,764
Public offering price (in dollars per share) \| $ / shares	$ 20.00
Net proceeds from IPO \| $	$ 306.5
Over-Allotment Option
Product Information [Line Items]
Sale of stock (in shares)	2,205,882

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