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Income Taxes - Schedule of Reconciliation of Beginning and Ending Amount Of Unrecognized Tax Benefits (Detail) - Rocket Lab USA, Inc. - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]    
Balance at beginning of year $ 800 $ 800
Increases (decreases) related to prior year tax positions 0 0
Balance at end of year $ 800 $ 800