Consolidated Condensed Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Securities available-for-sale, amortized cost	$ 1,079,745	$ 1,097,645
Securities held-to-maturity, fair value	$ 346,199	$ 363,779
Preferred Stock, Shares Authorized	200,000	200,000
Preferred Stock, Shares Issued	0	0
Common stock no par value	$ 0	$ 0
Common stock shares authorized	20,000,000	20,000,000
Common stock shares issued	16,150,740	16,150,752
Treasury stock shares	849,637	862,558