Fair Value Measurements - Book Value and Estimated Fair Value of Bank's Significant Financial Instruments Not Recorded at Fair Value (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Financial Assets:
Securities held-to-maturity	$ 400,852	$ 474,215
Financial Liabilities:
Time deposits	260,086	207,218
Securities sold under agreements to repurchase with retail customers	77,993	67,812
Book Value [Member]
Financial Assets:
Cash and due from banks	50,576	36,117
Securities held-to-maturity	392,932	469,417
Federal Home Loan Bank of New York stock	15,970	19,170
Loans receivable and mortgage loans held for sale	1,941,278	1,693,047
Financial Liabilities:
Deposits other than time deposits	1,707,685	1,512,917
Time deposits	260,086	207,218
Securities sold under agreements to repurchase with retail customers	77,993	67,812
Federal Home Loan Bank advances and other borrowings	260,506	332,738
Level 1 Inputs [Member]
Financial Assets:
Cash and due from banks	50,576	36,117
Financial Liabilities:
Securities sold under agreements to repurchase with retail customers	77,993	67,812
Level 2 Inputs [Member]
Financial Assets:
Securities held-to-maturity	400,852	474,215
Financial Liabilities:
Deposits other than time deposits	1,707,685	1,512,917
Time deposits	261,888	208,651
Federal Home Loan Bank advances and other borrowings	262,488	332,432
Level 3 Inputs [Member]
Financial Assets:
Federal Home Loan Bank of New York stock	15,970	19,170
Loans receivable and mortgage loans held for sale	$ 1,960,827	$ 1,709,819