Premises and Equipment - Summary of Premises and Equipment (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 597,571	$ 617,284
Accumulated depreciation	(134,775)	(126,359)
Premises and equipment, net	462,796	490,925
Land
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	72,182	79,569
Buildings
Property, Plant and Equipment [Line Items]
Buildings	367,658	380,925
Furniture, fixtures, and equipment
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	113,047	112,654
Leasehold improvements
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 44,684	$ 44,136