CONSOLIDATED STATEMENTS OF CONDITION (Parenthetical) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0	$ 0
Preferred stock, shares authorized	500,000	500,000
Preferred stock, liquidation preference per share	$ 1,000	$ 1,000
Common stock, stated value	$ 0.83	$ 0.83
Common stock, shares authorized	42,000,000	42,000,000
Common stock, shares issued	19,611,905	19,027,812
Common stock, shares outstanding	19,203,727	18,619,634
Treasury stock, shares	408,178	408,178