Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Investment securities:
Securities held to maturity, fair value (in dollars)	$ 2,492,686	$ 1,778,064
Shareholders' equity:
Common stock, par value (in dollars per share)	$ 2.50	$ 2.50
Common stock, shares authorized	160,000,000	160,000,000
Common stock, shares issued	75,641,322	69,332,297
Common stock, shares outstanding	75,641,322	69,332,297