Loans Receivable - Summary of Activity in Allowance for Loan Losses by Portfolio Segment (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Loans and Leases Receivable Disclosure [Line Items]
Allowance for Loan Losses, Beginning Allowance	$ 6,216	$ 4,943	$ 5,664	$ 4,904
Allowance for Loan Losses, Provision (credit)	2,008	7	2,755	71
Allowance for Loan Losses, Charge-offs	(9)	(11)	(223)	(141)
Allowance for Loan Losses, Recoveries	131	6	150	111
Allowance for Loan Losses, Ending Allowance	8,346	4,945	8,346	4,945
Commercial [Member]
Loans and Leases Receivable Disclosure [Line Items]
Allowance for Loan Losses, Beginning Allowance			3,853
Allowance for Loan Losses, Ending Allowance	5,792		5,792
Construction [Member]
Loans and Leases Receivable Disclosure [Line Items]
Allowance for Loan Losses, Beginning Allowance			159
Allowance for Loan Losses, Ending Allowance	446		446
Commercial Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Allowance for Loan Losses, Beginning Allowance			1,130
Allowance for Loan Losses, Ending Allowance	1,553		1,553
Home Equity Lines Of Credit [Member]
Loans and Leases Receivable Disclosure [Line Items]
Allowance for Loan Losses, Beginning Allowance			65
Allowance for Loan Losses, Ending Allowance	85		85
Consumer and Overdrafts [Member]
Loans and Leases Receivable Disclosure [Line Items]
Allowance for Loan Losses, Beginning Allowance			11
Allowance for Loan Losses, Ending Allowance	13		13
Originated [Member] \| Residential [Member]
Loans and Leases Receivable Disclosure [Line Items]
Allowance for Loan Losses, Beginning Allowance	352	379	363	386
Allowance for Loan Losses, Provision (credit)	102	8	86	(4)
Allowance for Loan Losses, Recoveries	3	2	8	7
Allowance for Loan Losses, Ending Allowance	457	389	457	389
Originated [Member] \| Commercial [Member]
Loans and Leases Receivable Disclosure [Line Items]
Allowance for Loan Losses, Beginning Allowance	4,568	3,261	3,853	3,073
Allowance for Loan Losses, Provision (credit)	1,099	(26)	1,814	276
Allowance for Loan Losses, Charge-offs				(114)
Allowance for Loan Losses, Recoveries	125		125
Allowance for Loan Losses, Ending Allowance	5,792	3,235	5,792	3,235
Originated [Member] \| Construction [Member]
Loans and Leases Receivable Disclosure [Line Items]
Allowance for Loan Losses, Beginning Allowance	273	258	159	505
Allowance for Loan Losses, Provision (credit)	173	(58)	287	(401)
Allowance for Loan Losses, Recoveries				96
Allowance for Loan Losses, Ending Allowance	446	200	446	200
Originated [Member] \| Commercial Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Allowance for Loan Losses, Beginning Allowance	953	880	1,130	780
Allowance for Loan Losses, Provision (credit)	600	69	573	169
Allowance for Loan Losses, Charge-offs			(150)
Allowance for Loan Losses, Recoveries		2		2
Allowance for Loan Losses, Ending Allowance	1,553	951	1,553	951
Originated [Member] \| Home Equity Lines Of Credit [Member]
Loans and Leases Receivable Disclosure [Line Items]
Allowance for Loan Losses, Beginning Allowance	60	82	65	80
Allowance for Loan Losses, Provision (credit)	23	(8)	10	(6)
Allowance for Loan Losses, Recoveries	2		10
Allowance for Loan Losses, Ending Allowance	85	74	85	74
Originated [Member] \| Consumer and Overdrafts [Member]
Loans and Leases Receivable Disclosure [Line Items]
Allowance for Loan Losses, Beginning Allowance	10	10
Allowance for Loan Losses, Provision (credit)	11	6
Allowance for Loan Losses, Charge-offs	(9)	(11)
Allowance for Loan Losses, Recoveries	1	2
Allowance for Loan Losses, Ending Allowance	13	7	13	7
Originated [Member] \| Consumer And Installment Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Allowance for Loan Losses, Beginning Allowance			11	7
Allowance for Loan Losses, Provision (credit)			37	21
Allowance for Loan Losses, Charge-offs			(42)	(27)
Allowance for Loan Losses, Recoveries			7	6
Allowance for Loan Losses, Ending Allowance	$ 13	7	13	7
Acquired [Member] \| Residential [Member]
Loans and Leases Receivable Disclosure [Line Items]
Allowance for Loan Losses, Beginning Allowance		73	83	73
Allowance for Loan Losses, Provision (credit)		16	(52)	16
Allowance for Loan Losses, Charge-offs			$ (31)
Allowance for Loan Losses, Ending Allowance		$ 89		$ 89

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

Name:	us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953423-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953423-111524

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)(1)(ii)
-URI http://asc.fasb.org/extlink&oid=118939070&loc=d3e15032-111544

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953423-111524

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB Topic 6.L.1)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74567-122707

+ Details

Name:	us-gaap_LoansAndLeasesReceivableAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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.

+ References

No definition available.

+ Details

Name:	us-gaap_LoansAndLeasesReceivableDisclosureLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of expense related to estimated loss from loan and lease transactions.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.11)
-URI http://asc.fasb.org/extlink&oid=116637391&loc=SL114874048-224260

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953423-111524

+ Details

Name:	us-gaap_ProvisionForLoanAndLeaseLosses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=pcsb_ConstructionPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=pcsb_HomeEquityPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=pcsb_ConsumerAndOverdraftsPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=pcsb_OriginatedLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=pcsb_ConsumerAndInstallmentLoansPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=pcsb_AcquiredLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: