CONSOLIDATED STATEMENTS OF CONDITION (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Available-for-sale securities, at amortized cost	$ 2,072,498	$ 1,599,894
Securities - held-to-maturity	268,283	0
Equity securities, at amortized cost	$ 910	$ 929
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)	14,695,105	14,964,389
Treasury stock, shares (in shares)	122,824	124,849