Loans and Allowance for Credit Losses - Troubled Debt Restructuring is 90 Days or More Past Due (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014 Contract	Jun. 30, 2013 Contract	Jun. 30, 2014 Contract	Jun. 30, 2013 Contract
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number of Contracts			2	4
Recorded Investment			$ 51	$ 18
Financing Receivable, Modification, Subsequent Default, Recorded Investment	6	5
Troubled Debt Restructuring Number Of Contracts Ninety Days Past Due	1	2
Residential real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Modification, Subsequent Default, Number of Contracts	1
Number of Contracts			2	1
Recorded Investment			51	9
Financing Receivable, Modification, Subsequent Default, Recorded Investment	6	0
Troubled Debt Restructuring Number Of Contracts Ninety Days Past Due		0
Loans to individuals [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Modification, Subsequent Default, Number of Contracts	0
Number of Contracts			0	3
Recorded Investment			0	9
Financing Receivable, Modification, Subsequent Default, Recorded Investment	$ 0	$ 5
Troubled Debt Restructuring Number Of Contracts Ninety Days Past Due		2