Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2025	Nov. 06, 2025
Document and Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2025
Document Transition Report	false
Entity Registrant Name	Concord Acquisition Corp II
Entity Incorporation, State or Country Code	DE
Entity File Number	001-40773
Entity Tax Identification Number	86-2171101
Entity Address, Address Line One	477 Madison Avenue
Entity Address, City or Town	New York
Entity Address State Or Province	NY
Entity Address, Postal Zip Code	10022
City Area Code	212
Local Phone Number	883-4330
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	true
Entity Central Index Key	0001851959
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2025
Document Fiscal Period Focus	Q3
Amendment Flag	false
Units, each consisting of one share of Class A common stock and one-third of one redeemable warrant
Document and Entity Information
Title of 12(b) Security	Units, each consisting of one share of Class A common stock and one-third of one redeemable warrant
Trading Symbol	CNDAU
Class A common stock, par value $0.0001 per share
Document and Entity Information
Title of 12(b) Security	Class A common stock, par value $0.0001 per share
Trading Symbol	CNDA
Entity Common Stock, Shares Outstanding		8,550
Redeemable warrants, each whole warrant exercisable for one share of Class A common stock at an exercise price of $11.50
Document and Entity Information
Title of 12(b) Security	Redeemable warrants, each whole warrant exercisable for one share of Class A common stock at an exercise price of $11.50
Trading Symbol	CNDAW
Class B common stock
Document and Entity Information
Entity Common Stock, Shares Outstanding		7,002,438

- Details

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Concord Acquisition Corp II 10-Q