CONSOLIDATED STATEMENTS OF CONDITION (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Available-for-sale securities, at amortized cost	$ 1,409,996	$ 1,442,724
Fair Value	$ 140,315	$ 142,832
Common Stock, par value (in dollars per share)	$ 0.10	$ 0.10
Common Stock, authorized (in shares)	25,000,000	25,000,000
Common Stock, issued (in shares)	15,301,524	15,171,816
Treasury stock, shares (in shares)	120,805	117,997