Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Allowance for loan losses	$ 12,814	$ 13,134
Preferred shares, no par value
Preferred shares, shares authorized	200,000	200,000
Preferred shares, liquidation preference	$ 1,000	$ 1,000
Preferred shares, shares issued	18,409	18,760
Common shares, no par value
Common shares, shares authorized	20,000,000	20,000,000
Common shares, shares issued	10,991,238	10,946,439
Treasury shares, common shares	747,964	747,964