CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Available-for-sale [Abstract]
Securities AFS, at estimated fair value	$ 1,409,568	$ 1,387,874
Held-to-maturity Securities, Other Disclosure Items [Abstract]
Securities held-to-maturity, fair value	$ 1,148,815	$ 1,149,156
Shareholders' equity:
Common stock, par value (in dollars per share)	$ 1.25	$ 1.25
Common stock, shares authorized (in shares)	80,000,000	80,000,000
Common stock, shares issued (in shares)	38,019,238	38,000,822
Shares purchased (in shares)	7,487,433	6,454,192