Recorded Investment in Home Equity, Consumer and Residential Mortgage Loans Based on Payment Activity (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 1,213,423	[1]	$ 1,129,305	[2]
Loans Acquired With Deteriorated Credit Quality	10,877		15,805
Home Equity Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	74,699	[1]	77,323	[2]
Loans Acquired With Deteriorated Credit Quality	0		0
Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	41,231	[1]	47,595	[2]
Loans Acquired With Deteriorated Credit Quality	148		164
Residential Mortgage Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	88,815	[1]	86,469	[2]
Loans Acquired With Deteriorated Credit Quality	149		152
Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	370		413
Performing [Member] | Home Equity Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	74,521		77,233
Performing [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	41,064		47,336
Performing [Member] | Residential Mortgage Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	88,558		85,721
Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	8,122		12,066
Nonperforming [Member] | Home Equity Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	178		90
Nonperforming [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	167		259
Nonperforming [Member] | Residential Mortgage Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 257		$ 748

[1] Total recorded investment in loans includes $5,522 in accrued interest.

[2] Total recorded investment in loans includes $5,756 in accrued interest.