Premises and Equipment - Summary of Premises and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total	$ 617,284	$ 594,483
Accumulated depreciation	(126,359)	(108,571)
Premises and equipment, net	490,925	485,912
Land [Member]
Property, Plant and Equipment [Line Items]
Total	79,569	79,231
Buildings [Member]
Property, Plant and Equipment [Line Items]
Total	380,925	365,102
Furniture, Fixtures, and Equipment [Member]
Property, Plant and Equipment [Line Items]
Total	112,654	107,862
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total	$ 44,136	$ 42,288