Premises and Equipment - Summary of Premises and Equipment (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Property, Plant and Equipment [Line Items]
Total	$ 515,449	$ 525,120
Accumulated depreciation	(94,583)	(95,498)
Premises and equipment, net	420,866	429,622	$ 198,065
Land [Member]
Property, Plant and Equipment [Line Items]
Total	69,484	71,769
Buildings [Member]
Property, Plant and Equipment [Line Items]
Total	317,582	322,165
Furniture, Fixtures, and Equipment [Member]
Property, Plant and Equipment [Line Items]
Total	100,489	102,631
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total	$ 27,894	$ 28,555