Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Consolidated Balance Sheets [Abstract]
Debt securities, available-for-sale, cost (in dollars)	$ 595,481	$ 604,999
Equity securities, available for sale, cost (in dollars)	35,762	30,253
Other investments, cost	3,763	3,763
Subordinated debt securities, unamortized debt issuance cost (in dollars)	$ 937	$ 949
Common stock, par value (in dollars per share)	$ 0.18	$ 0.18
Common stock, authorized shares	33,333,333	33,333,333
Common stock, issued shares	20,872,831	20,872,831
Treasury stock, shares	2,745,115	2,703,803