Fair Value Disclosures of Financial Assets and Liabilities - Book Value and Estimated Fair Value of Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012
Financial assets:
Cash and cash equivalents	$ 439,725	$ 484,426	$ 530,612	$ 500,887
Loans held for sale	17,131	31,491
Loans, net	2,956,769	2,904,976
Stock in Federal Home Loan Bank of Pittsburgh	33,578	35,869
Accrued interest receivable	10,715	10,798
Financial liabilities:
Deposits	3,173,082	3,186,942
Borrowed funds	21,858	24,739
Accrued interest payable	1,570	838
Book Value [Member]
Financial assets:
Investment securities	859,251	817,115
Book Value [Member] | Quoted Prices in Active Markets for Identical Asset (Level 1) [Member]
Financial assets:
Cash and cash equivalents	439,725	484,426
Book Value [Member] | Significant Unobservable Inputs (Level 3) [Member]
Financial assets:
Loans held for sale	17,131	31,491
Loans, net	2,956,769	2,904,976
Reverse mortgage loans	36,266	37,328
Financial liabilities:
Standby letters of credit	263	248
Book Value [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets:
Stock in Federal Home Loan Bank of Pittsburgh	33,578	35,869
Accrued interest receivable	10,715	10,798
Financial liabilities:
Deposits	3,173,082	3,186,942
Borrowed funds	924,318	903,831
Accrued interest payable	1,570	838
Fair Value [Member]
Financial assets:
Investment securities	859,251	817,115
Fair Value [Member] | Quoted Prices in Active Markets for Identical Asset (Level 1) [Member]
Financial assets:
Cash and cash equivalents	439,725	484,426
Fair Value [Member] | Significant Unobservable Inputs (Level 3) [Member]
Financial assets:
Loans held for sale	17,131	31,491
Loans, net	2,917,597	2,871,499
Reverse mortgage loans	36,266	37,328
Financial liabilities:
Standby letters of credit	263	248
Fair Value [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets:
Stock in Federal Home Loan Bank of Pittsburgh	33,578	35,869
Accrued interest receivable	10,715	10,798
Financial liabilities:
Deposits	2,979,368	2,982,420
Borrowed funds	925,739	904,804
Accrued interest payable	$ 1,570	$ 838