ORGANIZATION AND PRINCIPAL ACTIVITIES - Summary of principal subsidiaries and VIEs (Detail)	12 Months Ended
Dec. 31, 2020
Subsidiaries [Member] \| Jiayin Holdings Limited
Date of incorporation/establishment or acquisition	Jan. 31, 2018
Place of incorporation/establishment	BVI
Percentage of direct or indirect ownership	100.00%
Principal activities	Investment Holding
Subsidiaries [Member] \| Geerong(HK) Limited (formerly known as "Jiayin (HK) Limited")
Date of incorporation/establishment or acquisition	Jan. 31, 2018
Place of incorporation/establishment	Hong Kong
Percentage of direct or indirect ownership	100.00%
Principal activities	Investment Holding
Subsidiaries [Member] \| Jiayin Southeast Asia Holdings Limited
Date of incorporation/establishment or acquisition	Feb. 28, 2018
Place of incorporation/establishment	BVI
Percentage of direct or indirect ownership	100.00%
Principal activities	Investment Holding
Subsidiaries [Member] \| Shanghai Kunjia Technology Co., Ltd.
Date of incorporation/establishment or acquisition	Jun. 30, 2018
Place of incorporation/establishment	Shanghai
Percentage of direct or indirect ownership	100.00%
Principal activities	Investment Holding
Subsidiaries [Member] \| Geerong Yunke Information Technology Co., Ltd
Date of incorporation/establishment or acquisition	Jul. 31, 2019
Place of incorporation/establishment	Shanghai
Percentage of direct or indirect ownership	100.00%
Principal activities	Technology development and consumer finance services
Subsidiaries [Member] \| Geerong Yun (Shanghai) Enterprise Development Co., Ltd.
Date of incorporation/establishment or acquisition	Sep. 30, 2019
Place of incorporation/establishment	Shanghai
Percentage of direct or indirect ownership	100.00%
Principal activities	Technology development and consumer finance services
Subsidiaries [Member] \| Shanghai Chuangzhen Software Co., Ltd.
Date of incorporation/establishment or acquisition	Apr. 30, 2020
Place of incorporation/establishment	Shanghai
Percentage of direct or indirect ownership	100.00%
Principal activities	Technology service
Subsidiaries [Member] \| Aguila Information, S.A.P.I. de C.V.
Date of incorporation/establishment or acquisition	Jan. 31, 2020
Place of incorporation/establishment	Mexico
Percentage of direct or indirect ownership	51.00%
Principal activities	Lending business
Subsidiaries [Member] \| PT Jayindo Fintek Pratama
Date of incorporation/establishment or acquisition	Apr. 30, 2020
Place of incorporation/establishment	Indonesia
Percentage of direct or indirect ownership	85.00%
Principal activities	Lending business
Variable Interest Entity, Primary Beneficiary Shanghai Jiayin Finance Technology Co Ltd
Date of incorporation/establishment or acquisition	Jun. 30, 2015
Place of incorporation/establishment	Shanghai
Percentage of direct or indirect ownership	100.00%
Principal activities	Technology service
Variable Interest Entity, Primary Beneficiary Shanghai Jiajie Internet Finance Information Services Co Ltd
Date of incorporation/establishment or acquisition	Sep. 30, 2015
Place of incorporation/establishment	Shanghai
Percentage of direct or indirect ownership	100.00%
Principal activities	Technology development and consumer finance services
Variable Interest Entity, Primary Beneficiary Shanghai Niwodai Internet Finance Information Services Co Ltd
Date of incorporation/establishment or acquisition	Jul. 31, 2019
Place of incorporation/establishment	Shanghai
Percentage of direct or indirect ownership	100.00%
Principal activities	Technology development and consumer finance services

Date when an entity was incorporated

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- Definition

Entity Incorporation, State Country Name

+ References

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- Definition

Percentage of subsidiary's or equity method investee's stock owned by parent immediately after all stock transactions.

+ References

No definition available.

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- Definition

Description of the major products or services that a subsidiary or equity investee sells or provides and its principal markets, including locations of those markets.

+ References

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- Definition

Percentage of the Variable Interest Entity's (VIE) voting interest owned by (or beneficial interest in) the reporting entity (directly or indirectly).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 5A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121559654&loc=SL6759159-111685

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The overall reason that the Variable Interest Entity (VIE) was formed. For example, the VIE was formed to hold financial assets, including loans or receivables, real estate or other property or to engage in research and development or other activities on behalf of another company.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
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-Section 50
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