Common Stock - Additional Information (Detail)		1 Months Ended							3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 22, 2022 shares	Aug. 31, 2022 shares	Jul. 31, 2022 USD ($)	Jun. 30, 2022	May 31, 2022 USD ($) shares	Dec. 31, 2021 USD ($) $ / shares shares	Jun. 30, 2021 USD ($)	Feb. 28, 2021 USD ($) $ / shares shares	Sep. 30, 2022 USD ($) $ / shares shares	Mar. 31, 2022 USD ($)	Sep. 30, 2022 USD ($) $ / shares shares	Sep. 30, 2021 USD ($)	Dec. 31, 2020 USD ($) $ / shares shares	Nov. 02, 2022 shares	Oct. 30, 2022 shares	Feb. 08, 2022	Jun. 21, 2021 shares	Feb. 13, 2021 shares
Class of Stock [Line Items]
Common Stock, Shares Authorized | shares						4,003,595			300,000,000		300,000,000
Preferred Stock, Shares Authorized | shares									10,000,000		10,000,000
Stock Issued During Period, Shares, New Issues | shares											4,170,459
Proceeds From Share Subscription Facility Provided By Business Acquired											$ 125,000,000
Common Stock, Shares, Outstanding | shares						2,850,876			7,077,402		7,077,402
Class of Warrant or Right, Outstanding | shares									1,494,670		1,494,670
Proceeds From Convertible Debt											$ 0	$ 37,130,000
Adjustments to Additional Paid in Capital, Warrant Issued										$ 17,602,000
Change in fair value of the forward asset loss									$ 700,000		9,600,000
Short-term debt						$ 34,311,000			$ 0		$ 0
The Extension Notes [Member]
Class of Stock [Line Items]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares								314,901
Proceeds From Convertible Debt								$ 48,700,000
Public Warrants [Member]
Class of Stock [Line Items]
Class of Warrant or Right, Outstanding | shares									689,999		689,999
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares									$ 230.00		$ 230.00
Number of trading days for determining the share price											20 days
Number of consecutive trading days for determining the share price											30 days
Share Price | $ / shares									360.00		$ 360.00
Public Warrants [Member] | Share Price Equal or Exceeds Eighteen Rupees Per Dollar [Member]
Class of Stock [Line Items]
Share Price | $ / shares									$ 360.00		360.00
Class of warrants redemption price per unit | $ / shares											$ 0.20
Private Placement Warrants [Member]
Class of Stock [Line Items]
Class of Warrant or Right, Outstanding | shares									376,000		376,000
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares									$ 230.00		$ 230.00
Two Thousand And Twenty Three Notes Warrants [Member]
Class of Stock [Line Items]
Class of Warrant or Right, Outstanding | shares									258,775		258,775
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares									$ 0.20		$ 0.20
Class of warrants and rights issued during the period | shares													176,358
Class of warrants and rights issued price per warrant | $ / shares								$ 0.20					$ 0.20
Proceeds from Issuance of Private Placement													$ 16,100,000
Warrants and rights outstanding, expire period								March 2025					March 2025
Proceeds allocated to the common stock warrants								$ 22,000,000.0					$ 7,200,000
Sensata Warrants [Member]
Class of Stock [Line Items]
Class of Warrant or Right, Outstanding | shares																	125,000
Adjustments to Additional Paid in Capital, Warrant Issued							$ 17,600,000
Warrants exercised for cash							25,000
Sensata Warrants [Member] | Prepaid Expenses and Other Current Assets [Member]
Class of Stock [Line Items]
Sensata prepaid services							8,800,000
Sensata Warrants [Member] | Other Noncurrent Assets [Member]
Class of Stock [Line Items]
Sensata prepaid services							$ 8,800,000
GEM Warrants [Member]
Class of Stock [Line Items]
Class of Warrant or Right, Outstanding | shares									169,896		169,896
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares						$ 200.00			$ 200.00		$ 200.00
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares						169,896
GEM Agreement [Member]
Class of Stock [Line Items]
Stock Issued During Period, Shares, New Issues | shares		600,000
Percentage Price Used For Determining Average Closing Price						0.90
Proceeds From Share Subscription Facility Provided By Business Acquired						$ 125,000
Warrants Fair Value Disclosure									$ 4,000,000.0		$ 4,000,000.0
Warrants Payable In Cash											2,500,000
Unamortized deferred offering costs									2,300,000		2,300,000
Line Of Credit commitment fee											2,300,000
Warrants issued											4,000,000.0
Asset Fair Value									400,000		400,000
Number of trading days for determining the share price					30 days
Number of consecutive trading days for determining the share price	40 days		40 days
Draw down amount on GEM Agreement					$ 9,900,000
Shares issued upon draw down of GEM agreement | shares					1,314,159
Settlement of Share-settled forward			$ 10,000.0
Percentage of average trading price to determine other values.				90.00%	90.00%
Change in fair value of the forward asset loss									700,000		9,600,000
cash consideration									$ 1,700,000		$ 1,700,000
Common stock, shares returned upon settlement | shares	56,729								280,000		280,000
Warrant exercisable , percent											2.50%
Except Series B And Series C Convertible Preferred Stock (Legacy Quanergy) [Member]
Class of Stock [Line Items]
Common Stock Convertible Conversion Ratio									1,940		1,940
Series B Convertible Preferred Stock (Legacy Quanergy) [Member]
Class of Stock [Line Items]
Common Stock Convertible Conversion Ratio									5,771		5,771					0.5771
Series C Convertible Preferred Stock (Legacy Quanergy) [Member]
Class of Stock [Line Items]
Common Stock Convertible Conversion Ratio									7,155		7,155					0.7155
Common Class A [Member] | Prior to Business Combination [Member]
Class of Stock [Line Items]
Common Stock, Shares, Outstanding | shares									1,380,000		1,380,000							1,380,000
Subsequent Event [Member]
Class of Stock [Line Items]
Class of Warrant or Right, Outstanding | shares														2,940,000	2,940,000
Maximum [Member]
Class of Stock [Line Items]
Common Stock, Shares Authorized | shares									310,000,000		310,000,000