Loans, Allowance for Loan Losses, and Credit Quality Indicators - Summary of Allowance for Credit Losses Activity by Loan Segment (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance, beginning of period	$ 14,941	$ 16,570	$ 13,367
Charge-offs	(3,664)	(15,804)	(15,514)
Recoveries	3,168	1,275	3,717
Provision	1,900	12,900	15,000
Balance, end of period	16,345	14,941	16,570
Ending allowance: collectively evaluated for impairment	16,343	14,486
Ending allowance: individually evaluated for impairment	2	455
Total ending allowance	16,345	14,941
Ending loan balance: collectively evaluated for impairment	861,083	789,642
Ending loan balance: individually evaluated for impairment	10,174	31,187
Total Loans Receivable	871,257	820,829
Commercial and Other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance, beginning of period	2,776	2,230
Charge-offs	(1,401)	(1,403)
Recoveries	1,917	581
Provision	554	1,368
Balance, end of period	3,846	2,776
Ending allowance: collectively evaluated for impairment	3,844	2,776
Ending allowance: individually evaluated for impairment	2
Total ending allowance	3,846	2,776
Ending loan balance: collectively evaluated for impairment	322,677	267,099
Ending loan balance: individually evaluated for impairment	4,039	7,057
Total Loans Receivable	326,716	274,156
Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance, beginning of period	8,267	10,042
Charge-offs	(1,190)	(5,555)
Recoveries	55	176
Provision	2,324	3,604
Balance, end of period	9,456	8,267
Ending allowance: collectively evaluated for impairment	9,456	7,812
Ending allowance: individually evaluated for impairment		455
Total ending allowance	9,456	8,267
Ending loan balance: collectively evaluated for impairment	455,206	467,426
Ending loan balance: individually evaluated for impairment	6,034	11,040
Total Loans Receivable	461,240	478,466
Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance, beginning of period	2,104	3,040
Charge-offs	(1,054)	(8,792)
Recoveries	1,188	498
Provision	(251)	7,358
Balance, end of period	1,987	2,104
Ending allowance: collectively evaluated for impairment	1,987	2,104
Total ending allowance	1,987	2,104
Ending loan balance: collectively evaluated for impairment	79,619	50,548
Ending loan balance: individually evaluated for impairment	101	13,090
Total Loans Receivable	79,720	63,638
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance, beginning of period	87	64
Charge-offs	(19)	(54)
Recoveries	8	20
Provision	(6)	57
Balance, end of period	70	87
Ending allowance: collectively evaluated for impairment	70	87
Total ending allowance	70	87
Ending loan balance: collectively evaluated for impairment	3,581	4,569
Total Loans Receivable	3,581	4,569
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance, beginning of period	1,707	1,194
Provision	(721)	513
Balance, end of period	986	1,707
Ending allowance: collectively evaluated for impairment	986	1,707
Total ending allowance	$ 986	$ 1,707