Premises and Equipment - Summary of Premises and Equipment (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 593,850	$ 617,284
Accumulated depreciation	(131,486)	(126,359)
Premises and equipment, net	462,364	490,925
Land
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	71,451	79,569
Buildings
Property, Plant and Equipment [Line Items]
Buildings	360,462	380,925
Furniture, fixtures, and equipment
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	117,566	112,654
Leasehold improvements
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 44,371	$ 44,136