XML 58 R48.htm IDEA: XBRL DOCUMENT v3.7.0.1

Allowance for Loan Losses - Recorded Investment in Commercial Loan Classes by Internally Assigned Risk Ratings (Details) - Commercial - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 4,492,679	$ 4,355,395
Total percentage of recorded investment in commercial loan	100.00%	100.00%
Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 4,267,238	$ 4,169,721
Total percentage of recorded investment in commercial loan	95.00%	95.70%
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 135,698	$ 88,198
Total percentage of recorded investment in commercial loan	3.00%	2.00%
Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 89,743	$ 97,476
Total percentage of recorded investment in commercial loan	2.00%	2.30%
Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 2,664,642	$ 2,498,476
Total percentage of recorded investment in commercial loan	100.00%	100.00%
Commercial Real Estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 2,574,835	$ 2,423,742
Total percentage of recorded investment in commercial loan	96.60%	97.00%
Commercial Real Estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 57,197	$ 33,098
Total percentage of recorded investment in commercial loan	2.20%	1.30%
Commercial Real Estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 32,610	$ 41,636
Total percentage of recorded investment in commercial loan	1.20%	1.70%
Commercial and Industrial
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 1,401,283	$ 1,401,035
Total percentage of recorded investment in commercial loan	100.00%	100.00%
Commercial and Industrial | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 1,290,204	$ 1,315,507
Total percentage of recorded investment in commercial loan	92.10%	93.90%
Commercial and Industrial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 62,033	$ 40,409
Total percentage of recorded investment in commercial loan	4.40%	2.90%
Commercial and Industrial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 49,046	$ 45,119
Total percentage of recorded investment in commercial loan	3.50%	3.20%
Commercial Construction
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 426,754	$ 455,884
Total percentage of recorded investment in commercial loan	99.99%	100.00%
Commercial Construction | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 402,199	$ 430,472
Total percentage of recorded investment in commercial loan	94.20%	94.40%
Commercial Construction | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 16,468	$ 14,691
Total percentage of recorded investment in commercial loan	3.90%	3.20%
Commercial Construction | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 8,087	$ 10,721
Total percentage of recorded investment in commercial loan	1.90%	2.40%

X

- Definition

Loans and leases receivable gross carrying amount commercial percentage.

+ References

No definition available.

+ Details

Name:	stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage
Namespace Prefix:	stba_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

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

X

- 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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

+ Details

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

X

- Details

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

X

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=us-gaap_PassMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=us-gaap_SpecialMentionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=us-gaap_SubstandardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

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

X

- Details

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

X

- Details

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