Share-Based Compensation - Summary of the Option Unit Activity (Details)	6 Months Ended
Jun. 30, 2021 $ / shares shares
2021 Equity Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of units, exchange for options in the company	3,222,790
Number of units, grant outstanding ending balance	3,222,790
Number of units, vested	343,926
Number of units, unvested	2,878,864
Weighted average exercise price, issued in exchange for options in the company's parent \| $ / shares	$ 15.00
Weighted average exercise price, grant outstanding ending balance \| $ / shares	15.00
Weighted average exercise price, grants vested \| $ / shares	15.00
Weighted average exercise price, grants unvested \| $ / shares	$ 15.00
First Advantage Corporation [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of units, exchange for options in the company	3,938,491
Number of units, grant outstanding ending balance	3,938,491
Number of units, vested	367,615
Number of units, unvested	3,570,876
Weighted average exercise price, issued in exchange for options in the company's parent \| $ / shares	$ 6.65
Weighted average exercise price, grants vested \| $ / shares	6.61
Weighted average exercise price, grants unvested \| $ / shares	$ 6.66
Fastball Holdco L P [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of units, grant outstanding beginning balance	2,733,734
Number of units, exercised	(24,112)
Number of units, forfeited	(107,168)
Number of units, exchange for options in the company	(2,602,454)
Weighted average exercise price, grant outstanding beginning balance \| $ / shares	$ 10.06
Weighted average exercise price, exercised \| $ / shares	10.00
Weighted average exercise price, forefeited \| $ / shares	10.00
Weighted average exercise price, exchanged for options \| $ / shares	$ 10.07

Share based compensation arrangement By share based payment award options exchange for option in period.

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Share based compensation arrangements by share based payment award issued in exchanged for options in period weighted average exercise price.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Number of fully vested and expected to vest options outstanding that can be converted into shares under option plan. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted-average exercise price, at which grantee can acquire shares reserved for issuance, for fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Number of non-vested options outstanding.

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