Fair Value Measurements - Book Value and Estimated Fair Value of Bank's Significant Financial Instruments Not Recorded at Fair Value (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Financial Assets:
Securities held-to-maturity	$ 724,250	$ 598,119
Federal Home Loan Bank of New York stock, at cost	20,358	19,313
Financial Liabilities:
Time deposits	622,547	647,103
Securities sold under agreements to repurchase with retail customers	75,050	69,935
Book Value
Financial Assets:
Cash and due from banks	107,660	301,373
Securities held-to-maturity	720,511	598,691
Federal Home Loan Bank of New York stock, at cost	20,358	19,313
Loans receivable, net and mortgage loans held for sale	3,868,973	3,804,994
Financial Liabilities:
Deposits other than time deposits	3,554,362	3,540,647
Time deposits	622,547	647,103
Securities sold under agreements to repurchase with retail customers		69,935
Federal Home Loan Bank advances and other borrowings	334,164	307,057
Level 1 Inputs
Financial Assets:
Cash and due from banks	107,660	301,373
Securities held-to-maturity	8,670	8,550
Financial Liabilities:
Securities sold under agreements to repurchase with retail customers	75,050	69,935
Level 2 Inputs
Financial Assets:
Securities held-to-maturity	711,924	586,504
Financial Liabilities:
Deposits other than time deposits	3,554,362	3,540,647
Time deposits	618,396	644,354
Federal Home Loan Bank advances and other borrowings	332,729	304,901
Level 3 Inputs
Financial Assets:
Securities held-to-maturity	3,656	3,030
Federal Home Loan Bank of New York stock	20,358	19,313
Loans receivable, net and mortgage loans held for sale	$ 3,932,367	$ 3,834,677