Intangible Assets - Schedule of Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 411,624	$ 392,757
Core deposit premiums	5,846	7,603
Customer relationship and other intangibles	7,866	2,987
Mortgage servicing rights	941	1,075
Intangible assets	$ 426,277	$ 404,422