CONSOLIDATED STATEMENTS OF CONDITION (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Assets:
Available-for-sale investment securities, pledged amount	$ 393,453	$ 598,873
Amortized Cost	3,287,497	3,301,607
Held-to-maturity securities	1,131,615	1,121,816
Amortized cost	$ 69,892	$ 72,275
Shareholders' equity:
Preferred stock, par value (in dollars per share)	$ 1.00	$ 1.00
Preferred stock, shares authorized	500,000	500,000
Preferred stock, shares issued	0	0
Common stock, par value (in dollars per share)	$ 1.00	$ 1.00
Common stock, shares authorized	75,000,000	75,000,000
Common stock, shares issued	54,540,107	54,372,292
Treasury stock, shares at cost	1,775,546	1,045,232
Shares held by deferred compensation arrangements	100,870	120,556