Intangible Assets - Amortization Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Goodwill and Intangible Assets Disclosure [Abstract]
Core deposit premiums	$ 1,757	$ 1,472	$ 965
Customer relationship and other intangibles	2,136	1,106	335
Mortgage servicing rights	173	179	324
Amortization expenses of intangible assets	$ 4,066	$ 2,757	$ 1,624