LOANS AND LEASES (Schedule of Balances by Portfolio Class, Based on Impairment Method) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Total Loans Individually Evaluated for Impairment	$ 36,369	$ 35,924
Ending ALLL Attributable to Loans Individually Evaluated for Impairment	6,342	2,800
Total Loans Collectively Evaluated for Impairment	4,366,676	4,353,717
Ending ALLL Attributable to Loans Collectively Evaluated for Impairment	57,441	40,876
Total Loans	4,403,045	4,389,641
Total Ending ALLL	63,783	43,676	$ 38,653	$ 38,504
Residential Portfolio Segment [Member] \| Primary Residential Mortgages [Member]
Total Loans Individually Evaluated for Impairment	7,098	6,890
Ending ALLL Attributable to Loans Individually Evaluated for Impairment	58	215
Total Loans Collectively Evaluated for Impairment	549,955	571,416
Ending ALLL Attributable to Loans Collectively Evaluated for Impairment	3,115	1,875
Total Loans	557,053	578,306
Total Ending ALLL	3,173	2,090	3,477	3,506
Residential Portfolio Segment [Member] \| Home Equity Lines of Credit [Member]
Total Loans Individually Evaluated for Impairment	2	3
Total Loans Collectively Evaluated for Impairment	55,854	57,245
Ending ALLL Attributable to Loans Collectively Evaluated for Impairment	237	128
Total Loans	55,856	57,248
Total Ending ALLL	237	128	152	164
Residential Portfolio Segment [Member] \| Multifamily Property [Member]
Total Loans Collectively Evaluated for Impairment	1,203,487	1,210,003
Ending ALLL Attributable to Loans Collectively Evaluated for Impairment	9,104	6,037
Total Loans	1,203,487	1,210,003
Total Ending ALLL	9,104	6,037	5,768	5,959
Residential Portfolio Segment [Member] \| Junior Lien [Member]
Total Loans Individually Evaluated for Impairment	15	19
Total Loans Collectively Evaluated for Impairment	6,802	6,992
Ending ALLL Attributable to Loans Collectively Evaluated for Impairment	23	13
Total Loans	6,817	7,011
Total Ending ALLL	23	13	15	15
Commercial Real Estate Portfolio Segment [Member] \| Owner Occupied Property [Member]
Total Loans Individually Evaluated for Impairment	368	379
Total Loans Collectively Evaluated for Impairment	250,925	249,040
Ending ALLL Attributable to Loans Collectively Evaluated for Impairment	2,838	2,064
Total Loans	251,293	249,419
Total Ending ALLL	2,838	2,064	2,534	2,614
Commercial Real Estate Portfolio Segment [Member] \| Investment Property [Member]
Total Loans Individually Evaluated for Impairment	22,554	22,605
Ending ALLL Attributable to Loans Individually Evaluated for Impairment	4,000	1,000
Total Loans Collectively Evaluated for Impairment	1,069,740	1,072,577
Ending ALLL Attributable to Loans Collectively Evaluated for Impairment	23,671	14,988
Total Loans	1,092,294	1,095,182
Total Ending ALLL	27,671	15,988	14,410	14,248
Commercial Portfolio Segment [Member] \| Construction [Member]
Total Loans Collectively Evaluated for Impairment	3,137	5,520
Ending ALLL Attributable to Loans Collectively Evaluated for Impairment	40	27
Total Loans	3,137	5,520
Total Ending ALLL	40	27	1	1
Consumer and Other Loans [Member]
Total Loans Collectively Evaluated for Impairment	56,998	58,213
Ending ALLL Attributable to Loans Collectively Evaluated for Impairment	394	296
Total Loans	56,998	58,213
Total Ending ALLL	394	296	306	384
Commercial and Industrial Sector [Member] \| Commercial Portfolio Segment [Member]
Total Loans Individually Evaluated for Impairment	6,332	6,028
Ending ALLL Attributable to Loans Individually Evaluated for Impairment	2,284	1,585
Total Loans Collectively Evaluated for Impairment	898,617	861,267
Ending ALLL Attributable to Loans Collectively Evaluated for Impairment	14,840	12,768
Total Loans	904,949	867,295
Total Ending ALLL	17,124	14,353	10,185	9,839
Lease Financing [Member]
Total Loans Collectively Evaluated for Impairment	268,436	258,401
Ending ALLL Attributable to Loans Collectively Evaluated for Impairment	3,141	2,642
Total Loans	268,436	258,401
Total Ending ALLL	3,141	2,642
Agricultural Sector [Member]
Total Loans Collectively Evaluated for Impairment	2,725	3,043
Ending ALLL Attributable to Loans Collectively Evaluated for Impairment	38	38
Total Loans	2,725	3,043
Total Ending ALLL	$ 38	$ 38	$ 2	$ 2

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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 (g)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953423-111524

+ Details

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

- Definition

Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

+ References

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The balance of financing receivables that were collectively evaluated for impairment.

+ 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 (h)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953423-111524

+ Details

Name:	us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The balance of financing receivables that were individually evaluated for impairment.

+ 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 (h)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953423-111524

+ Details

Name:	us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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

Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes 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 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=118952595&loc=d3e4428-111522

+ Details

Name:	us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

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

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=pgc_PrimaryResidentialMortgagesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_HomeEquityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=pgc_MultifamilyPropertyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LienCategoryAxis=us-gaap_JuniorLienMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=pgc_OwnerOccupiedPropertyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=pgc_InvestmentPropertyMember
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_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConstructionLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_EquitySecuritiesByIndustryAxis=us-gaap_CommercialAndIndustrialSectorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_EquitySecuritiesByIndustryAxis=us-gaap_LeaseAgreementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_EquitySecuritiesByIndustryAxis=us-gaap_AgriculturalSectorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: