Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2021	Aug. 06, 2021
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Jun. 30, 2021
Entity File Number	001-39835
Entity Registrant Name	STAR PEAK CORP II
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	85-3374823
Entity Address, Address Line One	1603 Orrington Avenue, 13th Floor
Entity Address, City or Town	Evanston
Entity Address State Or Province	IL
Entity Address, Postal Zip Code	60201
City Area Code	847
Local Phone Number	905-4500
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	0001830210
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Amendment Flag	false
Transition Report	false
Unit Each Consisting Of One Class Common Stock And One Fourth Redeemable Warrant
Document Information [Line Items]
Title of 12(b) Security	Units, each consisting of one share of Class A common stock, $0.0001 par value, and one-fourth of one warrant
Trading Symbol	STPC.U
Security Exchange Name	NASDAQ
Class A Common Stock
Document Information [Line Items]
Title of 12(b) Security	Shares of Class A common stock included as part of the units
Trading Symbol	STPC
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		40,250,000
Warrants, each whole warrant exercisable for one share of Class A Common Stock at an exercise price of $11.50
Document Information [Line Items]
Title of 12(b) Security	Warrants included as part of the units, each whole warrant exercisable for one share of Class A common stock at an exercise price of $11.50
Trading Symbol	STPC WS
Security Exchange Name	NASDAQ
Class B Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		10,062,500