Premises and Equipment - Summary of Premises and Equipment (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016
Property, Plant and Equipment [Line Items]
Total	$ 513,084	$ 525,120
Accumulated depreciation	(99,151)	(95,498)
Premises and equipment, net	413,933	429,622	$ 231,656
Land [Member]
Property, Plant and Equipment [Line Items]
Total	67,989	71,769
Buildings [Member]
Property, Plant and Equipment [Line Items]
Total	314,273	322,165
Furniture, Fixtures, and Equipment [Member]
Property, Plant and Equipment [Line Items]
Total	102,431	102,631
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total	$ 28,391	$ 28,555