Reverse Recapitalization - Summary of Number of Legacy Quanergy Shares (Detail)	6 Months Ended
	Jun. 30, 2022 shares
Schedule Of Number Of Legacy Quanergy Shares [Line Items]
Shares issued upon exercise of options - 2021	197,875
Total	83,412,347
Legacy Quanergy Shares [Member]
Schedule Of Number Of Legacy Quanergy Shares [Line Items]
Balance at December 31, 2020	4,696,352
Shares issued upon exercise of options - 2021	20,000
Shares issued upon exercise of common stock warrants - 2021	2,324
Issuance of restricted stock awards	300,000
Total	71,485,143	[1]
Legacy Quanergy Shares With Exchange Ratio Effect [Member]
Schedule Of Number Of Legacy Quanergy Shares [Line Items]
Balance at December 31, 2020	18,221,534
Shares issued upon exercise of options - 2021	77,595
Shares issued upon exercise of common stock warrants - 2021	9,016
Issuance of restricted stock awards	1,163,984
Total	71,485,143
2023 Notes (Member) | Legacy Quanergy Shares [Member]
Schedule Of Number Of Legacy Quanergy Shares [Line Items]
Conversion of 2023 Notes into common stock, Shares	3,728,147	[2]
2023 Notes (Member) | Legacy Quanergy Shares With Exchange Ratio Effect [Member]
Schedule Of Number Of Legacy Quanergy Shares [Line Items]
Conversion of 2023 Notes into common stock, Shares	14,464,992	[2]
Convertible Preferred Stock [Member] | Legacy Quanergy Shares [Member]
Schedule Of Number Of Legacy Quanergy Shares [Line Items]
Recapitalization applied to Convertible Preferred Stock outstanding at December 31, 2020	7,695,112
Convertible Preferred Stock [Member] | Legacy Quanergy Shares With Exchange Ratio Effect [Member]
Schedule Of Number Of Legacy Quanergy Shares [Line Items]
Recapitalization applied to Convertible Preferred Stock outstanding at December 31, 2020	37,548,022

[1] (1) The number of Legacy Quanergy shares was determined as follows:

[2] (2) The 2023 Notes convert into shares of common stock of Quanergy at the rate consistent with the terms of note agreement.