Components of Other Intangible Assets, by Reporting Unit (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Finite-Lived Intangible Liabilities [Line Items]
Finite lived intangibles, net	$ 6,177us-gaap_FiniteLivedIntangibleAssetsNet
Total other intangible assets, net	6,421	2,866
Core deposit intangible assets
Finite-Lived Intangible Liabilities [Line Items]
Finite lived intangibles, gross	12,282	7,940
Accumulated amortization	(7,148)	(6,669)
Finite lived intangibles, net	5,134	1,271
Other Intangible Assets
Finite-Lived Intangible Liabilities [Line Items]
Finite lived intangibles, gross	4,246	4,246
Accumulated amortization	(2,959)	(2,651)
Finite lived intangibles, net	1,287	1,595
Community Banking
Finite-Lived Intangible Liabilities [Line Items]
Total other intangible assets, net	5,232	1,396
Community Banking \| Core deposit intangible assets
Finite-Lived Intangible Liabilities [Line Items]
Finite lived intangibles, gross	12,282	7,940
Accumulated amortization	(7,148)	(6,669)
Finite lived intangibles, net	5,134	1,271
Community Banking \| Other Intangible Assets
Finite-Lived Intangible Liabilities [Line Items]
Finite lived intangibles, gross	535	535
Accumulated amortization	(437)	(410)
Finite lived intangibles, net	98	125
Insurance Services
Finite-Lived Intangible Liabilities [Line Items]
Total other intangible assets, net	1,189	1,470
Insurance Services \| Other Intangible Assets
Finite-Lived Intangible Liabilities [Line Items]
Finite lived intangibles, gross	3,711	3,711
Accumulated amortization	(2,522)	(2,241)
Finite lived intangibles, net	$ 1,189	$ 1,470

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