Premises and Equipment - Schedule of Premises and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Land and improvements	$ 62,131	$ 66,609
Buildings and improvements	224,942	221,139
Furniture and equipment	106,501	102,171
Total cost	393,574	389,919
Accumulated depreciation and amortization	(200,214)	(187,437)
Right of use assets	56,061	58,532
Total premises and equipment, net	$ 249,421	$ 261,014