Securities (Narrative) (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012 Security	Dec. 31, 2011
Schedule Of Securities [Line Items]
Securities pledged to secure public deposits, trust deposits, and for other purposes, carrying value	$ 632,074	$ 547,727
Securities pledged as collateral for short-term borrowings, carrying value	780,941	680,212
Recover rate of banks	10.00%
Recover rate of insurance companies	15.00%
Number of pooled issue securities	26
Number of single issue securities	6
Estimated fair value of pooled trust preferred securities	21,144
Estimated fair value of single-issue trust preferred securities	7,899
Accretion income recognized by Corporation	1,080
Additional accretion income recognized	34
Accruing pooled trust preferred securities	4
Number of current pooled trust preferred securities	3
Interest income on pooled trust preferred securities	430
Number of pooled trust preferred securities sold	2
Remaining pooled trust securities	22
Number of pooled trust securities on which accretion income is recognized	14
Municipal bond portfolio, value	182,005
Percent of municipal bond portfolio rated A or better	99.40%
Percent of municipal bond portfolio, general obligation bonds	99.50%
Percent of municipal bonds from Pennsylvania	77.70%
Average holding size of municipal bond	1,000
Percent of portfolio with credit support	75.00%
Purchase of non-agency collateralized mortgage obligations from 2003 through 2005	161,151
Ratio of original average loan-to-value	66.10%
Original credit score	724
Non-agency collateralized mortgage obligations paydown balance on maturity	5,090
Annualized payout rate	35.50%
Credit-related loss recognized	226
Omega Financial Corporation [Member]
Schedule Of Securities [Line Items]
Retained non-agency collateralized mortgage obligations	60
Acquired Non Agency Commercial Mortgage Obligations	60
Parkvale [Member]
Schedule Of Securities [Line Items]
Retained non-agency collateralized mortgage obligations	4,238
Acquired Non Agency Commercial Mortgage Obligations	42,810
Residential Mortgage Backed Securities [Member]
Schedule Of Securities [Line Items]
Securities with unrealized losses for less than 12 months	4
Securities with unrealized losses of greater than 12 months	1
Agency Mortgage-Backed Securities [Member]
Schedule Of Securities [Line Items]
Securities with unrealized losses for less than 12 months	2
Non-Agency Collateralized Mortgage Obligations [Member]
Schedule Of Securities [Line Items]
Securities with unrealized losses for less than 12 months	2
Book value of non-agency collateralized mortgage obligations sold	$ 2,848
States Of The U.S. And Political Subdivisions [Member]
Schedule Of Securities [Line Items]
Securities with unrealized losses for less than 12 months	11
Collateralized Debt Obligations [Member]
Schedule Of Securities [Line Items]
Securities with unrealized losses for less than 12 months	11
Securities with unrealized losses of greater than 12 months	12
Equity Securities [Member]
Schedule Of Securities [Line Items]
Securities with unrealized losses for less than 12 months	2
Other Debt Obligations [Member]
Schedule Of Securities [Line Items]
Securities with unrealized losses of greater than 12 months	5
Senior Tranche [Member]
Schedule Of Securities [Line Items]
Number of single issue securities	1
Mezzanine Tranches [Member]
Schedule Of Securities [Line Items]
Number of pooled issue securities	25
Minimum [Member]
Schedule Of Securities [Line Items]
Deferral rates after the deferral period ends	10.00%
Range of credit loss	2.00%
Range of grown percentage of credit support due to paydowns and good credit performance	3.00%
Maximum [Member]
Schedule Of Securities [Line Items]
Deferral rates after the deferral period ends	90.00%
Range of credit loss	7.00%
Range of grown percentage of credit support due to paydowns and good credit performance	20.60%