Assets and Liabilities Measured at Fair Value on Recurring or Non-recurring Basis Using Significant Unobservable Inputs (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 23,746	$ 32,636
Impaired Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	18,564	23,462
Valuation Technique	Appraised Value/ Discounted Cash Flows Market Value of Note	Appraised Value/ Discounted Cash Flows Market Value of Note
Significant Unobservable Inputs	Appraisals and/or sales of comparable properties/ Independent quotes	Appraisals and/or sales of comparable properties/ Independent quotes
Impaired Loans | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Significant Unobservable Inputs, Range	0.00%	0.00%
Impaired Loans | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Significant Unobservable Inputs, Range	25.00%	25.00%
Other Real Estate Owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 5,182	$ 9,174
Valuation Technique	Appraised Value/ Comparable Sales/ Other Estimates from Independent Sources	Appraised Value/ Comparable Sales/ Other Estimates from Independent Sources
Significant Unobservable Inputs	Appraisals and/or sales of comparable properties/ Independent quotes	Appraisals and/or sales of comparable properties/ Independent quotes
Other Real Estate Owned | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Significant Unobservable Inputs, Range	0.00%	0.00%
Other Real Estate Owned | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Significant Unobservable Inputs, Range	40.00%	40.00%