CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Held to maturity, Fair Value	$ 82,126	$ 96,150
Allowance for loan losses	$ 21,202	$ 19,087
Preferred stock, par value
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value
Common stock, shares authorized	499,000,000	499,000,000
Common stock, shares issued	54,138,910	54,138,910
Common stock, shares outstanding	49,800,126	46,581,370
Treasury stock, shares	4,338,784	7,557,540