Credit Risk Profile by Internally Assigned Grade (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Residential	$ 9,432	[1]	$ 9,764	[1]
Consumer	32,425	[1]	33,798	[1]
Internally Assigned Grade | Pass Credit
Financing Receivable, Recorded Investment [Line Items]
Residential	7,382	[1]	7,905	[1]
Consumer	26,867	[1]	27,976	[1]
Internally Assigned Grade | Grade 6 Special Mention
Financing Receivable, Recorded Investment [Line Items]
Residential	398	[1]	732	[1]
Consumer	796	[1]	1,366	[1]
Internally Assigned Grade | Grade 7 Substandard
Financing Receivable, Recorded Investment [Line Items]
Residential	1,652	[1]	1,127	[1]
Consumer	$ 4,762	[1]	$ 4,456	[1]

[1] Credit quality indicators are reviewed and updated as applicable on an ongoing basis in accordance with credit policies.