Premises and Equipment (Premises and Equipment) (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Land	$ 107,249	$ 106,505
Buildings	379,829	361,573
Furniture and equipment	179,424	167,723
Leasehold improvements	74,314	67,540
Construction in progress	11,107	19,508
Premises and equipment, Gross	751,923	722,849
Less accumulated depreciation and amortization	(230,965)	(197,028)
Total premises and equipment, net	$ 520,958	$ 525,821