SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Mutual Holding Company Reorganization and Minority Stock Issuance (Details) - USD ($)		9 Months Ended
Jul. 17, 2019	Mar. 31, 2020
Mutual Holding Company Reorganization and Minority Stock Issuance
Net proceeds from sale of stock		$ 109,055,000
Stock contributed to Pioneer Bank Charitable Foundation (in shares)	519,554
Cash contributed to Pioneer Bank Charitable Foundation	$ 250,000
Pioneer Bancorp, MHC
Mutual Holding Company Reorganization and Minority Stock Issuance
Sale of stock (in shares)	14,287,723
Ownership interest (as a percent)		55.00%
Pioneer Bank ESOP
Mutual Holding Company Reorganization and Minority Stock Issuance
Numbers of shares owned by ESOP		1,018,325
Initial Public Offering
Mutual Holding Company Reorganization and Minority Stock Issuance
Sale of stock (in shares)	11,170,402
Share price	$ 10.00
Net proceeds from sale of stock	$ 109,100,000

The amount of cash contributed to the Pioneer Bank Charitable Foundation.

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The number of shares of common stock contributed to the Pioneer Bank Charitable Foundation.

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The cash inflow from the additional capital contribution to the entity.

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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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