Loans and Allowance for Credit Losses - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in nonperforming loans			$ (13,100,000)
Charge-offs	8,103,000	16,136,000	11,749,000	26,612,000
Decrease in specific allowance for nonperforming loans			2,800,000
Unfunded commitments related to nonperforming loans	3,300,000		3,300,000
Off balance sheet reserve to nonperforming loans	100,000		100,000
Loans held for sale	0		0
Total gains or losses included in earnings	77,000	257,000	77,000	383,000
Nonaccrual	35,721,000		35,721,000		45,888,000
Recorded investment	46,287,000		46,287,000		59,383,000
Troubled debt restructured loans decreased			13,100,000
Loans to individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non Accrual Status Of Loans After Number Of Days Past Due			150 days
Impaired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commitments related to troubled debt restructured loans increased			2,000,000
Loans with modifications to rate and payment due to reamortization	100,000	100,000	300,000	588,000
Loans Held For Sale [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gains or losses included in earnings	77,000	257,000	77,000	383,000
Audio Visual Equipment Distributer [Member] | Nonaccrual Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	4,300,000		4,300,000
Western Pennsylvania Specialty Metal Processor [Member] | Nonaccrual Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual	3,000,000		3,000,000
Non Accrual Loans [Member] | Local Energy Company [Member] [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual	10,600,000		10,600,000
Nonaccrual Loans Paid Off [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in nonperforming loans			12,500,000
Loans Sold [Domain]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in nonperforming loans			3,000,000
Additions to Nonperforming Loans [Domain]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in nonperforming loans			17,200,000
2012 Troubled Debt Restructuring [Member] | Non Accrual Loans [Member] | Local Energy Company [Member] [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual	2,700,000		2,700,000
2013 Troubled Debt Restructuring [Member] | Non Accrual Loans [Member] | Local Energy Company [Member] [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual	300,000		300,000
Nonaccrual Loans Paid Off [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Decrease In Troubled Debt Restructurings			11,300,000
Western Pennsylvania Funeral Home [Member] | Additions to Nonperforming Loans [Domain]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in nonperforming loans			700,000
Western Pennsylvania Personal Care Facility [Member] | Additions to Nonperforming Loans [Domain]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in nonperforming loans			700,000
Audio Visual Equipment Distributer [Member] | Additions to Nonperforming Loans [Domain]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in nonperforming loans			4,300,000
Residential Real Estate [Member] | Nonaccrual Loans Paid Off [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in nonperforming loans			900,000
Western Pennsylvania Real Estate Developer [Member] | Nonaccrual Loans Paid Off [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in nonperforming loans			4,700,000
Western Pennsylvania Reals Estate Investor [Member] | Nonaccrual Loans Paid Off [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in nonperforming loans			300,000
Western Pennsylvania Non-Profit Organization [Member] | Nonaccrual Loans Paid Off [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in nonperforming loans			3,100,000
Western Pennsylvania Reals Estate Manager [Member] | Nonaccrual Loans Paid Off [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in nonperforming loans			2,900,000
Western Pennsylvania Glass Manufacturer [Member] [Member] | Nonaccrual Loans Paid Off [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in nonperforming loans			600,000
Nonaccrual Consumer Loans [Member] | Additions to Nonperforming Loans [Domain]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in nonperforming loans			1,800,000
Commercial Real Estate Construction Project [Member] | Charge-offs [Domain]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charge-offs			300,000
Gas Drilling Related Business in Louisiana [Member] | Charge-offs [Domain]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charge-offs			5,800,000
Local Energy Company [Member] [Member] | Charge-offs [Domain]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charge-offs			500,000
Western Pennsylvania [Member] | Charge-offs [Domain]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charge-offs			600,000
Consumer Home Equity Loan [Member] | Charge-offs [Domain]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charge-offs			$ 400,000