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, 2013 Contract	Jun. 30, 2012 Contract	Jun. 30, 2013 Contract	Jun. 30, 2012 Contract
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number of Contracts			4	0
Recorded Investment			$ 18	$ 0
Residential Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number of Contracts				0
Recorded Investment			9	0
Financing Receivable, Modification, Subsequent Default, Number of Contracts			1
Consumer Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number of Contracts		0		0
Recorded Investment	$ 5	$ 0	$ 9	$ 0
Financing Receivable, Modification, Subsequent Default, Number of Contracts	2		3