CONDENSED CONSOLIDATED STATEMENTS OF CONDITION (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Available-for-sale securities, at amortized cost	$ 1,438,716	$ 1,442,724
Held-to-maturity securities, at fair value	$ 142,445	$ 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)	15,216,916	15,171,816
Treasury stock, shares (in shares)	115,445	117,997