Goodwill and Other Intangible Assets (Schedule of Other Intangible Assets) (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 42,791	$ 41,508
Accumulated Amortization	(34,644)	(30,904)
Future Amortization Expense, Total	8,147	10,604
Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	34,966	34,966
Accumulated Amortization	(29,670)	(26,732)
Future Amortization Expense, Total	5,296	8,234
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	6,839	5,975
Accumulated Amortization	(4,577)	(3,862)
Future Amortization Expense, Total	2,262	2,113
Noncompete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	986	567
Accumulated Amortization	(397)	(310)
Future Amortization Expense, Total	$ 589	$ 257