Premises and Equipment, Net - Components of Premises and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 587,096	$ 559,114
Accumulated depreciation and amortization	(288,153)	(276,117)
Total premises and equipment, net	298,943	282,997
Land [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	80,519	73,734
Buildings [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	211,923	199,960
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	70,314	74,965
Furniture and Equipment [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 224,340	$ 210,455