Common Stock - Additional Information (Detail)	1 Months Ended			3 Months Ended		12 Months Ended
	Dec. 31, 2021 USD ($) $ / shares shares	Jun. 30, 2021 USD ($) $ / shares shares	Feb. 28, 2021 USD ($) $ / shares shares	Mar. 31, 2022 USD ($) $ / shares shares	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($) $ / shares shares	Feb. 08, 2022	Feb. 13, 2021 shares
Class of Stock [Line Items]
Common Stock, Shares Authorized | shares	80,071,901			300,000,000
Preferred Stock, Shares Authorized | shares				10,000,000
Stock Issued During Period, Shares, New Issues | shares				83,412,347
Proceeds From Share Subscription Facility Provided By Business Acquired | $				$ 125,000,000
Common Stock, Shares, Outstanding | shares	57,020,151			98,498,731
Class of Warrant or Right, Outstanding | shares				34,135,794
Proceeds From Convertible Debt | $				$ 0	$ 37,186,000
Adjustments to Additional Paid in Capital, Warrant Issued | $				17,602,000	$ 21,971,000
Sensata prepaid services | $	$ 0			$ 8,801,000
The Extension Notes [Member]
Class of Stock [Line Items]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares			6,298,306
Proceeds From Convertible Debt | $			$ 48,700,000
Public Warrants [Member]
Class of Stock [Line Items]
Class of Warrant or Right, Outstanding | shares				13,799,988
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares				$ 11.50
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				$ 18.00
Public Warrants [Member] | Share Price Equal or Exceeds Eighteen Rupees Per Dollar [Member]
Class of Stock [Line Items]
Share Price | $ / shares				18.00
Class of warrants redemption price per unit | $ / shares				$ 0.01
Private Placement Warrants [Member]
Class of Stock [Line Items]
Class of Warrant or Right, Outstanding | shares				7,520,000
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares				$ 11.50
Two Thousand And Twenty Three Notes Warrants [Member]
Class of Stock [Line Items]
Class of Warrant or Right, Outstanding | shares				6,917,883
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares				$ 0.01
Class of warrants and rights issued during the period | shares						3,527,241
Class of warrants and rights issued price per warrant | $ / shares			$ 0.01			$ 0.01
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		2,500,000		2,500,000
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares				$ 0.01
Class of warrants and rights issued price per warrant | $ / shares		$ 0.01
Warrants and rights outstanding, expire period		June 2026
Adjustments to Additional Paid in Capital, Warrant Issued | $		$ 17,600,000
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				3,397,923
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares	$ 10.00			$ 10.00
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares	3,397,923
GEM Agreement [Member]
Class of Stock [Line Items]
Percentage Price Used For Determining Average Closing Price	90
Proceeds From Share Subscription Facility Provided By Business Acquired | $	$ 125,000,000
Warrants Fair Value Disclosure | $				$ 4,000,000.0
Warrants Payable In Cash | $				2,500,000
Deferred Offering Costs | $				2,500,000
Line Of Credit commitment fee | $				$ 2,500
Except Series B And Series C Convertible Preferred Stock (Legacy Quanergy) [Member]
Class of Stock [Line Items]
Common Stock Convertible Conversion Ratio				3.8799
Series B Convertible Preferred Stock (Legacy Quanergy) [Member]
Class of Stock [Line Items]
Common Stock Convertible Conversion Ratio				11.5423			11.5423
Series C Convertible Preferred Stock (Legacy Quanergy) [Member]
Class of Stock [Line Items]
Common Stock Convertible Conversion Ratio				14.3118			14.3118
Common Class A [Member] | Prior to Business Combination [Member]
Class of Stock [Line Items]
Common Stock, Shares, Outstanding | shares				27,600,000				27,600,000
Maximum [Member]
Class of Stock [Line Items]
Common Stock, Shares Authorized | shares				310,000,000