Goodwill and Other Intangible Assets (Schedule of Other Intangible Assets) (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 15,476	$ 45,906
Accumulated Amortization	(8,700)	(37,106)
Net Intangible Assets	6,776	8,800
Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	9,300	39,410
Accumulated Amortization	(4,002)	(32,324)
Net Intangible Assets	5,298	7,086
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	6,102	5,771
Accumulated Amortization	(4,692)	(4,214)
Net Intangible Assets	1,410	1,557
Noncompete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	74	725
Accumulated Amortization	(6)	(568)
Net Intangible Assets	$ 68	$ 157