Basis of Presentation (Policies)	9 Months Ended
Mar. 31, 2020
Accounting Policies [Abstract]
Nature of Operations	Nature of Operations: PCSB Financial Corporation (the “Holding Company” and together with its direct and indirect subsidiaries, the “Company”) is a Maryland corporation organized by PCSB Bank (the “Bank”) for the purpose of acquiring all of the capital stock of the Bank issued in the Bank's conversion to stock ownership on April 20, 2017. At March 31, 2020, the significant assets of the Holding Company were the capital stock of the Bank, cash deposited in the Bank, and a loan to the PCSB Bank Employee Stock Ownership Plan (“ESOP”). The liabilities of the Holding Company were insignificant. The Company is subject to the financial reporting requirements of the Securities Exchange Act of 1934, as amended and regulation and examination by the Board of Governors of the Federal Reserve System (the “Federal Reserve Board”) and the New York State Department of Financial Services (the “NYSDFS”). PCSB Bank is a community-oriented financial institution that provides financial services to individuals and businesses within its market area of Putnam, Southern Dutchess, Rockland and Westchester Counties in New York. The Bank is a state-chartered commercial bank and its deposits are insured up to applicable limits by the Deposit Insurance Fund of the Federal Deposit Insurance Corporation (“FDIC”). The Bank’s primary regulators are the FDIC and the NYSDFS.
Basis of Presentation	Basis of Presentation: The unaudited consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”), and include the accounts of the Holding Company, the Bank and the Bank's two subsidiaries – PCSB Funding Corp. and UpCounty Realty Corp. (formerly PCSB Realty Ltd.). PCSB Funding Corp. is a real estate investment trust that holds certain mortgage assets. UpCounty Realty Corp. is a corporation that holds certain properties foreclosed upon by the Bank. All intercompany transactions and balances have been eliminated in consolidation. The unaudited consolidated financial statements contained herein reflect all normal recurring adjustments that are, in the opinion of management, necessary for a fair presentation of the results for the interim periods presented. Such adjustments are the only adjustments reflected in the consolidated financial statements contained herein. The results of operations for the current period presented are not necessarily indicative of the results of operations that may be expected for the entire current fiscal year. Certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to the rules and regulations of the Securities and Exchange Commission. The accompanying unaudited consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto for the year ended June 30, 2019, included in the Company's Annual Report on Form 10-K. Certain prior period amounts have been reclassified to conform to the current presentation. Reclassifications had no effect on prior period net income or equity.
Risks and Uncertainties	Risks and Uncertainties: The COVID-19 pandemic has created extensive disruptions to the global and U.S. economies and to the lives of individuals throughout the world. The New York City Metropolitan area and environs have the highest incidence of COVID-19 in the nation, and the neighboring Tri-State area of New Jersey and Connecticut also has been particularly affected by COVID-19. Governments, businesses, and the public are taking unprecedented actions to contain the spread of COVID-19 and to mitigate its effects, including quarantines, travel bans, shelter-in-place orders, closures of businesses and schools, fiscal and monetary stimulus, and legislation designed to deliver financial aid and other relief. While the scope, duration, and full effects of COVID-19 are rapidly evolving and not fully known, the pandemic and the efforts to contain it have disrupted global economic activity, adversely affected the functioning of financial markets, impacted market interest rates, increased economic and market uncertainty, and disrupted trade and supply chains. The potential financial impact is unknown at this time. However, if these actions are sustained, it may adversely impact several industries within our geographic footprint and impair the ability of the Company’s customers to fulfill their contractual obligations to the Company. This could cause the Company to experience a material adverse effect on our business operations, asset valuations, financial condition, and results of operations. Material adverse impacts may include all or a combination of valuation impairments the Company’s intangible assets, investments, loans, or deferred tax assets. As it relates to the allowance for loan losses, the current quarter provision for loan losses includes a $1.7 million increase in qualitative reserves as the Company assessed the economic impacts the COVID-19 pandemic has had on our local economy and loan portfolio. The Company has taken actions to identify, assess and address its COVID-19 related credit exposure. Many factors are unknown, including the length of the resulting economic shutdown imposed by New York State and other neighboring states, the impacts of the government’s fiscal and monetary relief measures, including payment deferral programs, as well as the long-term impacts COVID-19 may have on our consumer and commercial borrowers. It is reasonably possible that the Company’s allowance for loan loss estimate as of March 31, 2020 will change in the near term and could result in a material change to the Company’s provision for loan losses, earnings and capital.
Use of Estimates	Use of Estimates: To prepare financial statements in conformity with GAAP management makes estimates and assumptions based on available information. These estimates and assumptions affect the amounts reported in the financial statements and the disclosures provided, and actual results could differ.
Recent Accounting Pronouncements	The pronouncements discussed below are not intended to be an all-inclusive list, but rather only those pronouncements that could potentially have a material impact on our financial position, results of operations or disclosures. Accounting Standards Adopted in the Period In February 2016, the FASB issued ASU 2016-02 “Leases.” ASU 2016-02 affects any entity that enters into a lease and is intended to increase the transparency and comparability of financial statements among organizations. The ASU requires, among other changes, a lessee to recognize on its balance sheet a lease asset and a lease liability for those leases longer than 12 months previously classified as operating leases. The lease asset would represent the right to use the underlying asset for the lease term and the lease liability would represent the discounted value of the required lease payments to the lessor. The ASU also requires entities to disclose key information about leasing arrangements. The Company currently leases eleven branches and two administrative offices. The Company adopted this standard and the related amendments (collectively "ASC 842") on July 1, 2019 and utilized the modified retrospective approach provided by ASU 2018-11, "Leases (Topic 842): Targeted Improvements," that allowed for a cumulative effect adjustment in the period of adoption. Under this method of adoption, the comparative information in the consolidated financial statements has not been revised and continues to be reported under the previously applicable lease accounting guidance (ASC 840). We also utilized the package of practical expedients permitted under the transition guidance which included the carry-forward of historical lease classification. The Company recorded a right to use asset totaling $11.9 million and lease liability totaling $12.0 million on the balance sheet for Company’s outstanding lease obligations on July 1, 2019. The right to use asset is disclosed within premises and equipment and the lease liability is disclosed within other liabilities on the balance sheet. In January 2017, the FASB issued ASU 2017-04 “Intangibles – Goodwill and Other (Topic 350).” ASU 2017-04 simplifies the test for goodwill impairment, which eliminates the second step in the goodwill impairment test which requires an entity to determine the implied fair value of the reporting unit’s goodwill. Instead, an entity should recognize an impairment loss if the carrying value of the net assets assigned to the reporting unit exceeds the fair value of the reporting unit, with the impairment loss not to exceed the amount of goodwill allocated to the reporting unit. The adoption of ASU 2017-04 on July 1, 2019 did not have a material impact on the Company’s consolidated financial statements. In March 2017, the FASB issued ASU 2017-08 "Receivables - Non-Refundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities." The ASU requires premiums on callable debt securities to be amortized to the earliest call date. The amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. The adoption of ASU 2017-08 on July 1, 2019 did not have a material impact on the Company’s consolidated financial statements. Future Application of Accounting Pronouncements Previously Issued In June 2016, the FASB issued ASU 2016-13 “Measurement of Credit Losses on Financial Instruments.” ASU 2016-13 affects entities holding financial assets that are not accounted for at fair value through net income, including loans, debt securities, and other financial assets. The ASU requires financial assets measured at amortized cost basis to be presented at the net amount expected to be collected by recording an allowance for current expected credit losses. In October 2019, the FASB unanimously voted to delay the implementation of the standard for three years for certain companies, including small reporting companies (as defined by the SEC), non-SEC public companies and private companies. The Company currently qualifies as a small reporting company and is subject to the delayed implementation. Therefore, the amendments in this update will be effective for the Company for the fiscal year beginning on July 1, 2023, including interim periods within that fiscal year. The Company is actively working through the provisions of the Update. Management has established a steering committee which is identifying the methodologies and the additional data requirements necessary to implement the Update and has engaged a third-party software service provider to assist in the Company's implementation. Management is currently evaluating the impact that ASU 2016-13 will have on the Company’s consolidated financial position, results of operations and disclosures.

Basis of Presentation (Policies)

9 Months Ended

Mar. 31, 2020

Nature of Operations: PCSB Financial Corporation (the “Holding Company” and together with its direct and indirect subsidiaries, the “Company”) is a Maryland corporation organized by PCSB Bank (the “Bank”) for the purpose of acquiring all of the capital stock of the Bank issued in the Bank's conversion to stock ownership on April 20, 2017. At March 31, 2020, the significant assets of the Holding Company were the capital stock of the Bank, cash deposited in the Bank, and a loan to the PCSB Bank Employee Stock Ownership Plan (“ESOP”). The liabilities of the Holding Company were insignificant. The Company is subject to the financial reporting requirements of the Securities Exchange Act of 1934, as amended and regulation and examination by the Board of Governors of the Federal Reserve System (the “Federal Reserve Board”) and the New York State Department of Financial Services (the “NYSDFS”).

PCSB Bank is a community-oriented financial institution that provides financial services to individuals and businesses within its market area of Putnam, Southern Dutchess, Rockland and Westchester Counties in New York. The Bank is a state-chartered commercial bank and its deposits are insured up to applicable limits by the Deposit Insurance Fund of the Federal Deposit Insurance Corporation (“FDIC”). The Bank’s primary regulators are the FDIC and the NYSDFS.

Basis of Presentation

Basis of Presentation: The unaudited consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”), and include the accounts of the Holding Company, the Bank and the Bank's two subsidiaries – PCSB Funding Corp. and UpCounty Realty Corp. (formerly PCSB Realty Ltd.). PCSB Funding Corp. is a real estate investment trust that holds certain mortgage assets. UpCounty Realty Corp. is a corporation that holds certain properties foreclosed upon by the Bank. All intercompany transactions and balances have been eliminated in consolidation.

The unaudited consolidated financial statements contained herein reflect all normal recurring adjustments that are, in the opinion of management, necessary for a fair presentation of the results for the interim periods presented. Such adjustments are the only adjustments reflected in the consolidated financial statements contained herein. The results of operations for the current period presented are not necessarily indicative of the results of operations that may be expected for the entire current fiscal year. Certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to the rules and regulations of the Securities and Exchange Commission. The accompanying unaudited consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto for the year ended June 30, 2019, included in the Company's Annual Report on Form 10-K.

Certain prior period amounts have been reclassified to conform to the current presentation. Reclassifications had no effect on prior period net income or equity.

Risks and Uncertainties

Risks and Uncertainties:

The COVID-19 pandemic has created extensive disruptions to the global and U.S. economies and to the lives of individuals throughout the world. The New York City Metropolitan area and environs have the highest incidence of COVID-19 in the nation, and the neighboring Tri-State area of New Jersey and Connecticut also has been particularly affected by COVID-19. Governments, businesses, and the public are taking unprecedented actions to contain the spread of COVID-19 and to mitigate its effects, including quarantines, travel bans, shelter-in-place orders, closures of businesses and schools, fiscal and monetary stimulus, and legislation designed to deliver financial aid and other relief. While the scope, duration, and full effects of COVID-19 are rapidly evolving and not fully known, the pandemic and the efforts to contain it have disrupted global economic activity, adversely affected the functioning of financial markets, impacted market interest rates, increased economic and market uncertainty, and disrupted trade and supply chains.

The potential financial impact is unknown at this time. However, if these actions are sustained, it may adversely impact several industries within our geographic footprint and impair the ability of the Company’s customers to fulfill their contractual obligations to the Company. This could cause the Company to experience a material adverse effect on our business operations, asset valuations, financial condition, and results of operations. Material adverse impacts may include all or a combination of valuation impairments the Company’s intangible assets, investments, loans, or deferred tax assets.

As it relates to the allowance for loan losses, the current quarter provision for loan losses includes a $1.7 million increase in qualitative reserves as the Company assessed the economic impacts the COVID-19 pandemic has had on our local economy and loan portfolio. The Company has taken actions to identify, assess and address its COVID-19 related credit exposure. Many factors are unknown, including the length of the resulting economic shutdown imposed by New York State and other neighboring states, the impacts of the government’s fiscal and monetary relief measures, including payment deferral programs, as well as the long-term impacts COVID-19 may have on our consumer and commercial borrowers. It is reasonably possible that the Company’s allowance for loan loss estimate as of March 31, 2020 will change in the near term and could result in a material change to the Company’s provision for loan losses, earnings and capital.

Use of Estimates

Use of Estimates: To prepare financial statements in conformity with GAAP management makes estimates and assumptions based on available information. These estimates and assumptions affect the amounts reported in the financial statements and the disclosures provided, and actual results could differ.

Recent Accounting Pronouncements

The pronouncements discussed below are not intended to be an all-inclusive list, but rather only those pronouncements that could potentially have a material impact on our financial position, results of operations or disclosures.

Accounting Standards Adopted in the Period

In February 2016, the FASB issued ASU 2016-02 “Leases.” ASU 2016-02 affects any entity that enters into a lease and is intended to increase the transparency and comparability of financial statements among organizations. The ASU requires, among other changes, a lessee to recognize on its balance sheet a lease asset and a lease liability for those leases longer than 12 months previously classified as operating leases. The lease asset would represent the right to use the underlying asset for the lease term and the lease liability would represent the discounted value of the required lease payments to the lessor. The ASU also requires entities to disclose key information about leasing arrangements. The Company currently leases eleven branches and two administrative offices. The Company adopted this standard and the related amendments (collectively "ASC 842") on July 1, 2019 and utilized the modified retrospective approach provided by ASU 2018-11, "Leases (Topic 842): Targeted Improvements," that allowed for a cumulative effect adjustment in the period of adoption. Under this method of adoption, the comparative information in the consolidated financial statements has not been revised and continues to be reported under the previously applicable lease accounting guidance (ASC 840). We also utilized the package of practical expedients permitted under the transition guidance which included the carry-forward of historical lease classification. The Company recorded a right to use asset totaling $11.9 million and lease liability totaling $12.0 million on the balance sheet for Company’s outstanding lease obligations on July 1, 2019. The right to use asset is disclosed within premises and equipment and the lease liability is disclosed within other liabilities on the balance sheet.

In January 2017, the FASB issued ASU 2017-04 “Intangibles – Goodwill and Other (Topic 350).” ASU 2017-04 simplifies the test for goodwill impairment, which eliminates the second step in the goodwill impairment test which requires an entity to determine the implied fair value of the reporting unit’s goodwill. Instead, an entity should recognize an impairment loss if the carrying value of the net assets assigned to the reporting unit exceeds the fair value of the reporting unit, with the impairment loss not to exceed the amount of goodwill allocated to the reporting unit. The adoption of ASU 2017-04 on July 1, 2019 did not have a material impact on the Company’s consolidated financial statements.

In March 2017, the FASB issued ASU 2017-08 "Receivables - Non-Refundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities." The ASU requires premiums on callable debt securities to be amortized to the earliest call date. The amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. The adoption of ASU 2017-08 on July 1, 2019 did not have a material impact on the Company’s consolidated financial statements.

Future Application of Accounting Pronouncements Previously Issued

In June 2016, the FASB issued ASU 2016-13 “Measurement of Credit Losses on Financial Instruments.” ASU 2016-13 affects entities holding financial assets that are not accounted for at fair value through net income, including loans, debt securities, and other financial assets. The ASU requires financial assets measured at amortized cost basis to be presented at the net amount expected to be collected by recording an allowance for current expected credit losses. In October 2019, the FASB unanimously voted to delay the implementation of the standard for three years for certain companies, including small reporting companies (as defined by the SEC), non-SEC public companies and private companies. The Company currently qualifies as a small reporting company and is subject to the delayed implementation. Therefore, the amendments in this update will be effective for the Company for the fiscal year beginning on July 1, 2023, including interim periods within that fiscal year. The Company is actively working through the provisions of the Update. Management has established a steering committee which is identifying the methodologies and the additional data requirements necessary to implement the Update and has engaged a third-party software service provider to assist in the Company's implementation. Management is currently evaluating the impact that ASU 2016-13 will have on the Company’s consolidated financial position, results of operations and disclosures.