Loans, Allowance for Loan Losses, and Credit Quality Indicators - Analysis of Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Financing Receivable, Impaired [Line Items]
Recorded Investment	$ 10,174	$ 31,187
Unpaid Principal Balance	17,178	45,716
Related Allowance	2	455
Average Recorded Investment	21,701	47,291	66,510
Interest Income Recognized	34	548	2,602
Commercial and other [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	4,039	7,057
Unpaid Principal Balance	9,546	10,691
Related Allowance	2
Average Recorded Investment	5,204	7,528
Interest Income Recognized	2	44
Consumer loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment
Unpaid Principal Balance
Interest Income Recognized
Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	6,034	11,040
Unpaid Principal Balance	7,459	12,336
Related Allowance		455
Average Recorded Investment	8,089	18,715
Interest Income Recognized	32	121
Real Estate [Member] | Multi-family residential [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance
Related Allowance
Average Recorded Investment		54
Interest Income Recognized
Real Estate [Member] | Residential 1-4 family [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,447	4,515
Unpaid Principal Balance	2,032	5,004
Related Allowance		10
Average Recorded Investment	3,086	6,136
Interest Income Recognized		52
Real Estate [Member] | Owner-occupied commercial [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	4,229	5,569
Unpaid Principal Balance	5,069	5,909
Related Allowance		445
Average Recorded Investment	4,838	6,647
Interest Income Recognized	21	36
Real Estate [Member] | Nonowner-occupied commercial [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	358	525
Unpaid Principal Balance	358	1,011
Average Recorded Investment	165	5,082
Interest Income Recognized	11
Real Estate [Member] | Other real estate loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment		431
Unpaid Principal Balance		412
Related Allowance
Average Recorded Investment		796
Interest Income Recognized		33
Construction [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	101	13,090
Unpaid Principal Balance	173	22,689
Average Recorded Investment	8,408	21,048
Interest Income Recognized		383
Construction [Member] | Multi-family residential [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance
Related Allowance
Average Recorded Investment		136
Interest Income Recognized
Construction [Member] | Residential 1-4 family [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment		757
Unpaid Principal Balance		1,037
Related Allowance
Average Recorded Investment	544	1,793
Interest Income Recognized
Construction [Member] | Aged Analysis of Loans Receivable [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment		2,568
Unpaid Principal Balance		3,306
Related Allowance
Average Recorded Investment	1,219	3,161
Interest Income Recognized		111
Construction [Member] | Commercial bare land and acquisition & development [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment		7,837
Unpaid Principal Balance		13,027
Related Allowance
Average Recorded Investment	5,621	12,617
Interest Income Recognized		234
Construction [Member] | Residential bare land and acquisition & development [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	101	1,928
Unpaid Principal Balance	173	5,319
Related Allowance
Average Recorded Investment	1,024	3,341
Interest Income Recognized		38
With no related allowance recorded [Member] | Commercial and other [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	3,921	7,057
Unpaid Principal Balance	9,417	10,691
Related Allowance
Average Recorded Investment	5,056	6,137
Interest Income Recognized	2	44
With no related allowance recorded [Member] | Consumer loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment
Unpaid Principal Balance
Related Allowance
Interest Income Recognized
With no related allowance recorded [Member] | Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	6,034	9,210
Unpaid Principal Balance	7,459	10,474
Average Recorded Investment	7,378	17,840
Interest Income Recognized	32	121
With no related allowance recorded [Member] | Real Estate [Member] | Multi-family residential [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment
Unpaid Principal Balance
Related Allowance
Average Recorded Investment		54
Interest Income Recognized
With no related allowance recorded [Member] | Real Estate [Member] | Residential 1-4 family [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,447	4,300
Unpaid Principal Balance	2,032	4,756
Related Allowance
Average Recorded Investment	3,068	5,785
Interest Income Recognized		52
With no related allowance recorded [Member] | Real Estate [Member] | Owner-occupied commercial [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	4,229	3,954
Unpaid Principal Balance	5,069	4,295
Related Allowance
Average Recorded Investment	4,157	6,220
Interest Income Recognized	21	36
With no related allowance recorded [Member] | Real Estate [Member] | Nonowner-occupied commercial [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	358	525
Unpaid Principal Balance	358	1,011
Related Allowance
Average Recorded Investment	153	5,052
Interest Income Recognized	11
With no related allowance recorded [Member] | Real Estate [Member] | Other real estate loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment		431
Unpaid Principal Balance		412
Related Allowance
Average Recorded Investment		729
Interest Income Recognized		33
With no related allowance recorded [Member] | Construction [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	101	13,090
Unpaid Principal Balance	173	22,689
Average Recorded Investment	8,408	19,487
Interest Income Recognized		383
With no related allowance recorded [Member] | Construction [Member] | Multi-family residential [Member]
Financing Receivable, Impaired [Line Items]
Related Allowance
Average Recorded Investment		136
With no related allowance recorded [Member] | Construction [Member] | Residential 1-4 family [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment		757
Unpaid Principal Balance		1,037
Related Allowance
Average Recorded Investment	544	1,331
Interest Income Recognized
With no related allowance recorded [Member] | Construction [Member] | Aged Analysis of Loans Receivable [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment		2,568
Unpaid Principal Balance		3,306
Related Allowance
Average Recorded Investment	1,219	3,161
Interest Income Recognized		111
With no related allowance recorded [Member] | Construction [Member] | Commercial bare land and acquisition & development [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment		7,837
Unpaid Principal Balance		13,027
Related Allowance
Average Recorded Investment	5,621	12,617
Interest Income Recognized		234
With no related allowance recorded [Member] | Construction [Member] | Residential bare land and acquisition & development [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	101	1,928
Unpaid Principal Balance	173	5,319
Related Allowance
Average Recorded Investment	1,024	2,242
Interest Income Recognized		38
With an allowance recorded [Member] | Commercial and other [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	118
Unpaid Principal Balance	129
Related Allowance	2
Average Recorded Investment	148	1,391
Interest Income Recognized
With an allowance recorded [Member] | Consumer loans [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance
Interest Income Recognized
With an allowance recorded [Member] | Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment		1,830
Unpaid Principal Balance		1,862
Related Allowance		455
Average Recorded Investment	711	875
With an allowance recorded [Member] | Real Estate [Member] | Multi-family residential [Member]
Financing Receivable, Impaired [Line Items]
Related Allowance
Interest Income Recognized
With an allowance recorded [Member] | Real Estate [Member] | Residential 1-4 family [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment		215
Unpaid Principal Balance		248
Related Allowance		10
Average Recorded Investment	18	351
Interest Income Recognized
With an allowance recorded [Member] | Real Estate [Member] | Owner-occupied commercial [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment		1,615
Unpaid Principal Balance		1,614
Related Allowance		445
Average Recorded Investment	681	427
Interest Income Recognized
With an allowance recorded [Member] | Real Estate [Member] | Nonowner-occupied commercial [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment
Unpaid Principal Balance
Related Allowance
Average Recorded Investment	12	30
Interest Income Recognized
With an allowance recorded [Member] | Real Estate [Member] | Other real estate loans [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment		67
Interest Income Recognized
With an allowance recorded [Member] | Construction [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment		1,561
With an allowance recorded [Member] | Construction [Member] | Multi-family residential [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance
Related Allowance
Interest Income Recognized
With an allowance recorded [Member] | Construction [Member] | Residential 1-4 family [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment
Average Recorded Investment		462
With an allowance recorded [Member] | Construction [Member] | Aged Analysis of Loans Receivable [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance
Related Allowance
Interest Income Recognized
With an allowance recorded [Member] | Construction [Member] | Commercial bare land and acquisition & development [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment
Unpaid Principal Balance
With an allowance recorded [Member] | Construction [Member] | Residential bare land and acquisition & development [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance
Related Allowance
Average Recorded Investment		1,099
Interest Income Recognized