Intangible Assets - Schedule of Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 420,562	$ 411,600
Core deposit premiums	1,753	2,539
Customer relationship and other intangibles	14,142	3,410
Mortgage servicing rights	562	629
Total intangible assets	$ 437,019	$ 418,178