Loans, Allowance for Loan Losses, and Credit Quality Indicators - Dental Credit Quality Indicators (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	$ 871,257	$ 820,829
Real estate loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	461,240	478,466
Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	79,720	63,638
Multi-family residential [Member] | Real estate loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	45,212	51,897
Multi-family residential [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	17,022	2,574
Residential 1-4 family [Member] | Real estate loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	51,437	61,717
Residential 1-4 family [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	20,390	17,960
Owner-occupied commercial [Member] | Real estate loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	219,276	207,008
Nonowner-occupied commercial [Member] | Real estate loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	145,315	157,844
Aged Analysis of Loans Receivable [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	23,235	10,901
Commercial bare land and acquisition & development [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	10,668	19,496
Residential bare land and acquisition & development [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	8,405	12,707
Commercial and other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	326,716	274,156
Consumer loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	3,581	4,569
Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	833,673	764,739
Pass [Member] | Real estate loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	437,816	451,224
Pass [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	75,063	44,614
Pass [Member] | Multi-family residential [Member] | Real estate loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	43,883	50,547
Pass [Member] | Multi-family residential [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	17,022	2,574
Pass [Member] | Residential 1-4 family [Member] | Real estate loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	43,458	51,622
Pass [Member] | Residential 1-4 family [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	20,278	14,036
Pass [Member] | Owner-occupied commercial [Member] | Real estate loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	208,713	194,250
Pass [Member] | Nonowner-occupied commercial [Member] | Real estate loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	141,762	154,805
Pass [Member] | Aged Analysis of Loans Receivable [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	21,646	7,075
Pass [Member] | Commercial bare land and acquisition & development [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	10,668	11,000
Pass [Member] | Residential bare land and acquisition & development [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	5,449	9,929
Pass [Member] | Commercial and other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	317,250	264,415
Pass [Member] | Consumer loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	3,544	4,486
Special Mention [Member] | Multi-family residential [Member] | Real estate loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade
Special Mention [Member] | Multi-family residential [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade
Special Mention [Member] | Owner-occupied commercial [Member] | Real estate loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade
Special Mention [Member] | Aged Analysis of Loans Receivable [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade
Special Mention [Member] | Residential bare land and acquisition & development [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade
Special Mention [Member] | Commercial and other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	37,584	54,397
Substandard [Member] | Real estate loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	23,424	25,627
Substandard [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	4,657	19,024
Substandard [Member] | Multi-family residential [Member] | Real estate loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	1,329	1,350
Substandard [Member] | Residential 1-4 family [Member] | Real estate loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	7,979	10,095
Substandard [Member] | Residential 1-4 family [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	112	3,924
Substandard [Member] | Owner-occupied commercial [Member] | Real estate loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	10,563	11,143
Substandard [Member] | Nonowner-occupied commercial [Member] | Real estate loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	3,553	3,039
Substandard [Member] | Aged Analysis of Loans Receivable [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	1,589	3,826
Substandard [Member] | Commercial bare land and acquisition & development [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade		8,496
Substandard [Member] | Residential bare land and acquisition & development [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	2,956	2,778
Substandard [Member] | Commercial and other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	9,466	9,663
Substandard [Member] | Consumer loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade	37	83
Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade		1,693
Doubtful [Member] | Real estate loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade		1,615
Doubtful [Member] | Multi-family residential [Member] | Real estate loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade
Doubtful [Member] | Multi-family residential [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade
Doubtful [Member] | Owner-occupied commercial [Member] | Real estate loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade		1,615
Doubtful [Member] | Aged Analysis of Loans Receivable [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade
Doubtful [Member] | Residential bare land and acquisition & development [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade
Doubtful [Member] | Commercial and other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade		78
Doubtful [Member] | Consumer loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loan Grade