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Stock-based Compensation - Disclosure - Stock-based Compensation - Summary of Weighted-average Assumptions (Detail) - $ / shares			12 Months Ended
	Sep. 30, 2020	Sep. 29, 2020	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value per share of common stock	$ 10.14	$ 10.12
Expected volatility	15.00%	15.00%
Risk-free interest rate	0.30%	0.30%
Expected life (years)	7 months 6 days	7 months 6 days
Rocket Lab USA, Inc.
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value per share of common stock			$ 12.80	$ 11.84
Expected volatility			60.00%	60.00%
Risk-free interest rate, minimum				1.90%
Risk-free interest rate, maximum				2.50%
Risk-free interest rate			0.60%
Expected life (years)			6 days 6 hours	6 days 6 hours
Dividend rate			0.00%	0.00%

X

- Definition

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iii)
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- Definition

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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- Definition

The risk-free interest rate assumption that is used in valuing an option on its own shares.

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-Publisher FASB
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- Definition

The maximum risk-free interest rate assumption that is used in valuing an option on its own shares.

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The minimum risk-free interest rate assumption that is used in valuing an option on its own shares.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Price of a single share of a number of saleable stocks of a company.

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Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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