Consolidated Statements of Financial Condition (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Interest-bearing deposits in banks and other financial institutions, collateral	$ 3,380	$ 3,380
Available-for-sale securities, amortized cost basis	816,114	807,761
Held-to-maturity securities, fair value	163,397	163,232
Allowance for loan losses	$ 40,201	$ 39,751
Common stock, shares authorized (in shares)	65,000,000	65,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, issued (in shares)	56,217,643	55,995,219
Treasury stock, shares (in shares)	24,807,145	24,605,145