Unaudited Condensed Consolidated Statements of Financial Condition (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Amortized cost of investment securities available for sale	$ 303,154	$ 300,028
Estimated fair value of investment securities held to maturity	250	250
Allowance for loans receivable	$ 15,716	$ 15,541
Preferred stock, par value	$ 1	$ 1
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 5	$ 5
Common stock, shares authorized	40,000,000	40,000,000
Common stock, shares issued	19,132,414	19,030,704
Common stock, shares outstanding	19,057,379	18,922,726
Treasury stock, shares	75,035	107,978