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Fair Value Disclosures of Financial Assets (Book Value And Estimated Fair Value of Financial instruments) (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2010
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 447,100	$ 468,017	$ 463,553	$ 376,759
Loans held for sale	20,905	10,185
Loans, net	2,656,161	2,702,589
Stock in Federal Home Loan Bank of Pittsburgh	30,172	35,756
Accrued interest receivable	10,292	11,743
Deposits	3,159,804	3,135,304
Borrowed funds	29,942	67,927
Accrued interest payable	6,335	1,910
Book Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities	922,645	871,794
Book Value [Member] \| Quoted Prices In Active Markets For Identical Asset (Level1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	447,100	468,017
Book Value [Member] \| Significant Unobservable Inputs (Level3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	20,905	10,185
Loans, net	2,656,161	2,702,589
Standby letters of credit	257	322
Book Value [Member] \| Significant Other Observable Inputs (Level2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stock in Federal Home Loan Bank of Pittsburgh	30,171	35,756
Accrued interest receivable	10,292	11,743
Deposits	3,159,804	3,135,304
Borrowed funds	644,823	723,620
Accrued interest payable	6,335	1,910
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities	922,645	871,794
Fair Value [Member] \| Quoted Prices In Active Markets For Identical Asset (Level1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	447,100	468,017
Fair Value [Member] \| Significant Unobservable Inputs (Level3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	20,905	10,185
Loans, net	2,677,467	2,721,804
Standby letters of credit	257	322
Fair Value [Member] \| Significant Other Observable Inputs (Level2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stock in Federal Home Loan Bank of Pittsburgh	30,171	35,756
Accrued interest receivable	10,292	11,743
Deposits	3,079,661	3,087,464
Borrowed funds	650,389	731,522
Accrued interest payable	$ 6,335	$ 1,910