Reverse Recapitalization - Summary of Number of Legacy Quanergy Shares (Detail)	9 Months Ended
	Sep. 30, 2022 shares
Schedule Of Number Of Legacy Quanergy Shares [Line Items]
Shares issued upon exercise of options - 2021	14,741
Total	4,170,459
Legacy Quanergy Shares [Member]
Schedule Of Number Of Legacy Quanergy Shares [Line Items]
Balance at December 31, 2020	234,785
Shares issued upon exercise of options - 2021	999
Shares issued upon exercise of common stock warrants - 2021	115
Issuance of restricted stock awards	14,999
Total	3,574,099	[1]
Legacy Quanergy Shares With Exchange Ratio Effect [Member]
Schedule Of Number Of Legacy Quanergy Shares [Line Items]
Balance at December 31, 2020	911,017
Shares issued upon exercise of options - 2021	3,878
Shares issued upon exercise of common stock warrants - 2021	448
Issuance of restricted stock awards	58,199
Total	3,574,099
2023 Notes (Member) | Legacy Quanergy Shares [Member]
Schedule Of Number Of Legacy Quanergy Shares [Line Items]
Conversion of 2023 Notes into common stock, Shares	186,380	[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	723,223	[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	1,877,334

[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.