Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Amortized cost of securities available-for-sale	$ 1,028,883	$ 1,097,645
Fair value of securities held-to-maturity	$ 351,422	$ 363,779
Preferred stock, shares authorized	200,000	200,000
Preferred stock, shares issued	0	0
Preferred stock per share liquidation preference	$ 0	$ 0
Common stock, no par value	$ 0	$ 0
Common stock, shares authorized	20,000,000	20,000,000
Common stock stock, shares issued	16,586,165	16,150,752
Treasury stock, shares	887,987	862,558