Goodwill and Other Intangible Assets - Schedule of Mortgage Servicing Rights at Carrying Value (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Acquired Finite-Lived Intangible Assets
Gross carrying amount	$ 79,594	$ 57,665
Accumulated amortization	(43,305)	(37,304)
Net carrying amount	36,289	20,361
Mortgage Servicing Rights
Acquired Finite-Lived Intangible Assets
Gross carrying amount	6,110	4,751
Accumulated amortization	(2,021)	(1,253)
Net carrying amount	$ 4,089	$ 3,498