Loans and Allowance for Credit Losses - Additional Information (Detail) (USD $)	12 Months Ended					12 Months Ended				12 Months Ended								12 Months Ended			3 Months Ended	12 Months Ended															12 Months Ended				12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Water Treatment Plant [Member]	Dec. 31, 2012 Gas Well Servicing Operation [Member]	Dec. 31, 2013 Commercial real estate loans [Member]	Dec. 31, 2012 Troubled debt restructured loans [Member]	Dec. 31, 2012 Commercial real estate [Member]	Dec. 31, 2012 Commercial real estate [Member] Gas Well Servicing Operation [Member]	Dec. 31, 2013 Impaired Loans [Member]	Dec. 31, 2013 Non Accrual Loans [Member]	Dec. 31, 2013 Unallocated [Member]	Dec. 31, 2012 Unallocated [Member]	Dec. 31, 2011 Unallocated [Member]	Dec. 31, 2013 Consumer Loan [Member]	Dec. 31, 2013 Western Pennsylvania Non-Profit Corporation [Member] Impaired Loans [Member]	Dec. 31, 2013 Impaired Loans [Member]	Dec. 31, 2013 Western Pennsylvania Non-Profit Healthcare Facility [Member]	Dec. 31, 2013 Western Pennsylvania Student Housing Project [Member]	Dec. 31, 2013 Local Energy Company [Member]	Jun. 30, 2013 Western Pennsylvania Real Estate Developer [Member]	Dec. 31, 2013 Western Pennsylvania Real Estate Developer [Member]	Dec. 31, 2013 Western Pennsylvania Real Estate Developer [Member] Impaired Loans [Member]	Dec. 31, 2013 Real Estate Developer In Eastern Pennsylvania [Member] Impaired Loans [Member]	Dec. 31, 2013 Commercial Real Estate Loan in Nevada [Member] Impaired Loans [Member]	Dec. 31, 2013 Construction Loan In Florida [Member] Impaired Loans [Member]	Dec. 31, 2013 Hotel Resort Syndication Loan in the State of Washington [Member] Accruing Loans [Member]	Dec. 31, 2013 Western Pennsylvania Specialty Plastics Molding Company [Member] Accruing Loans [Member]	Dec. 31, 2013 Western Pennsylvania Excavation Company [Member] Accruing Loans [Member]	Dec. 31, 2013 Four Commercial Loans [Member]	Dec. 31, 2013 Nonaccrual Commercial Loans [Member]	Dec. 31, 2013 Nonaccrual Consumer Loans [Member]	Dec. 31, 2013 Western Pennsylvania Specialty Metal Processor [Member]	Dec. 31, 2013 Western Pennsylvania Glass Manufacturer [Member] Nonaccrual Commercial Loans [Member]	Dec. 31, 2013 Western Pennsylvania Specialty Metal Processor [Member] Nonaccrual Commercial Loans [Member]	Dec. 31, 2013 Western Pennsylvania Reals Estate Manager [Member] Nonaccrual Commercial Loans [Member]	Dec. 31, 2013 Western Pennsylvania Real Estate Developer [Member] Nonaccrual Commercial Loans [Member]	Dec. 31, 2013 Local Energy Company [Member] Nonaccrual Commercial Loans [Member]	Jun. 30, 2012 Local Energy Company [Member] Nonaccrual Commercial Loans [Member]	Dec. 31, 2013 Reserve for Off-balance Sheet Activities [Member] Impaired Loans [Member]	Dec. 31, 2013 Loans Held for Sale [Member]	Dec. 31, 2012 Loans Held for Sale [Member]	Dec. 31, 2013 Residential real estate [Member] Contract	Dec. 31, 2012 Commercial real estate [Member] Contract	Dec. 31, 2011 Commercial real estate [Member] Contract
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non Accrual Status Of Loans After Number Of Days Past Due															150 days
Increase In Commitments Related To Troubled Debt Restructured Loans										$ (1,100,000)
Troubled Debt Restructured Loans Decreased										33,500,000
Provision for credit losses	19,227,000	20,544,000	55,816,000									(5,926,000)	1,090,000	(109,000)
Charge-offs	35,178,000	16,969,000	68,293,000				5,600,000					0	0	0				2,800,000	3,000,000	2,300,000	13,100,000	13,100,000	28,500,000							21,200,000							500,000
Transfer to Other Real Estate																																					4,800,000
Decrease in nonperforming loans										(48,200,000)	42,200,000													(17,200,000)	(2,500,000)	(3,500,000)	3,800,000	2,100,000	2,300,000
Amount Of Non Accrual Status Loan																															32,800,000	3,700,000		3,100,000	3,600,000		5,700,000	12,700,000
Decrease In Specific Allowance For Nonperforming Loans										9,000,000
Recorded Investment	59,383,000	107,555,000
Nonaccrual loans				2,800,000	3,700,000			3,300,000	17,000,000
Unfunded commitments related to nonperforming loans										519,000													800,000
Off balance sheet reserve to nonperforming loans																																								100,000
Nonaccrual	45,888,000	94,518,000														3,100,000	2,400,000																3,300,000			7,700,000		12,300,000
Financing receivable recorded investment nonaccrual status remaining portion																							44,100,000
Loan maturity extension								6 months
Charge-Off Recognized Related to Loans Held for Sale						2,700,000
Loans held for sale	0
Total gains or losses included in earnings	(770,000)	2,409,000																																							625,000	2,870,000
Troubled debt restructured Loan							10,200,000																																3,300,000
Loans with modification to rate and payment due to amortization	2,000,000	4,700,000	25,200,000
Minimum days required for conversion of trouble debt to be in default	90 days
Financing Receivable, Modification, Subsequent Default, Number of Contracts																																											1	0	1
Financing Receivable, Modification, Subsequent Default, Recorded Investment																																											$ 19,000		$ 4,134,000