CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Securities held-to-maturity, fair value	$ 2,733,059	$ 2,775,184
Allowance for credit losses - securities held-to-maturity	$ (1,708)	$ (1,707)
Preferred stock, par value (in dollars per share)	$ 0	$ 0
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	225,000	225,000
Preferred stock, shares outstanding (in shares)	225,000	225,000
Preferred Stock, Liquidation Preference Per Share	$ 1,000	$ 1,000
Common stock, par value (in dollars per share)	$ 1.00	$ 1.00
Common stock, shares authorized (in shares)	180,000,000	180,000,000
Common stock, shares issued (in shares)	77,219,000	76,767,000
Common stock, shares outstanding (in shares)	77,219,000	76,767,000