Consideration Paid and Fair Value of Identifiable Assets Acquired and Liabilities Assumed, Davidson Trust Company (Detail) (USD $) In Thousands, unless otherwise specified			1 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	May 15, 2012 Davidson Trust Company	May 15, 2012 Davidson Trust Company Customer relationships	May 15, 2012 Davidson Trust Company Non competition agreements	May 15, 2012 Davidson Trust Company brand
Business Acquisition [Line Items]
Cash			$ 9,450
Contingent payment liability			1,050
Value of consideration			10,500
Cash operating accounts			1,433
Other assets			201
Intangible asset				3,720	1,385	970
Premises and equipment			117
Deferred tax asset			839
Total assets			8,665
Deferred tax liability			2,125
Miscellaneous liabilities			885
Total liabilities			3,010
Net assets acquired			5,655
Goodwill resulting from acquisition of DTC	$ 32,843	$ 32,897	$ 4,845