Fair Value Disclosures of Financial Assets and Liabilities - Book Value and Estimated Fair Value of Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
Financial assets:
Cash and cash equivalents	$ 475,189	$ 484,426	$ 537,522	$ 500,887
Loans held for sale	35,188	31,491
Loans, net	2,993,361	2,904,976
Stock in Federal Home Loan Bank of Pittsburgh	37,587	35,869
Accrued interest receivable	11,004	10,798
Financial liabilities:
Deposits	3,153,329	3,186,942
Borrowed funds	18,455	24,739
Accrued interest payable	2,381	838
Quoted Prices in Active Markets for Identical Asset (Level 1) [Member]
Financial assets:
Loans held for sale
Significant Unobservable Inputs (Level 3) [Member]
Financial assets:
Loans held for sale
Significant Other Observable Inputs (Level 2) [Member]
Financial assets:
Loans held for sale	35,188
Book Value [Member]
Financial assets:
Investment securities	841,706	817,115
Book Value [Member] | Quoted Prices in Active Markets for Identical Asset (Level 1) [Member]
Financial assets:
Cash and cash equivalents	475,189	484,426
Book Value [Member] | Significant Unobservable Inputs (Level 3) [Member]
Financial assets:
Loans held for sale	35,188	31,491
Loans, net	2,993,361	2,904,976
Reverse mortgage loans	32,543	37,328
Financial liabilities:
Standby letters of credit	185	248
Book Value [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets:
Stock in Federal Home Loan Bank of Pittsburgh	37,587	35,869
Accrued interest receivable	11,004	10,798
Financial liabilities:
Deposits	3,153,329	3,186,942
Borrowed funds	984,866	903,831
Accrued interest payable	2,381	838
Fair Value [Member]
Financial assets:
Investment securities	841,706	817,115
Fair Value [Member] | Quoted Prices in Active Markets for Identical Asset (Level 1) [Member]
Financial assets:
Cash and cash equivalents	475,189	484,426
Fair Value [Member] | Significant Unobservable Inputs (Level 3) [Member]
Financial assets:
Loans held for sale	35,188	31,491
Loans, net	2,964,818	2,871,499
Reverse mortgage loans	32,543	37,328
Financial liabilities:
Standby letters of credit	185	248
Fair Value [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets:
Stock in Federal Home Loan Bank of Pittsburgh	37,587	35,869
Accrued interest receivable	11,004	10,798
Financial liabilities:
Deposits	2,962,149	2,982,420
Borrowed funds	986,520	904,804
Accrued interest payable	$ 2,381	$ 838