Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Securities available for sale, amortized cost	$ 7,190,161	$ 5,766,234
Securities held to maturity, fair value	1,420,107	1,467,581
Property and equipment, accumulated depreciation	266,239	271,801
Right of use assets, accumulated amortization	$ 28,589	$ 23,330
Preferred stock, par value per share	$ 20.00	$ 20.00
Common stock, par value per share	$ 3.33	$ 3.33