Loans - Summary of Aging and Non-Accrual Loans by Class (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	$ 2,946	$ 1,913
60-89 Days Past Due	4,518	2,646
90 Days or More Past Due	9,384	11,055
Total Past Due	16,848	15,614
Current	271,133	291,262
90-days Past Due and Still Accruing	792
Non- accrual Loans	10,853	13,264
Commercial And Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	1,518	1,228
60-89 Days Past Due	28	367
90 Days or More Past Due	269
Total Past Due	1,815	1,595
Current	25,261	25,225
90-days Past Due and Still Accruing	792
Non- accrual Loans	1,547	977
Commercial real estate, Owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	355	121
60-89 Days Past Due	99
90 Days or More Past Due	2,475	2,610
Total Past Due	2,929	2,731
Current	58,116	65,438
90-days Past Due and Still Accruing
Non- accrual Loans	2,475	2,610
Commercial real estate, Non-owner occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due
60-89 Days Past Due	1,801	992
90 Days or More Past Due
Total Past Due	1,801	992
Current	62,756	68,449
90-days Past Due and Still Accruing
Non- accrual Loans
Construction/Land, Residential construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due
60-89 Days Past Due
90 Days or More Past Due	1,351	540
Total Past Due	1,351	540
Current	16,037	14,219
90-days Past Due and Still Accruing
Non- accrual Loans	559	540
Construction/land, Other construction & land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	165
60-89 Days Past Due	983	1,225
90 Days or More Past Due	4,866	5,988
Total Past Due	6,014	7,213
Current	18,076	17,204
90-days Past Due and Still Accruing
Non- accrual Loans	5,849	7,139
Residential Real Estate, Equity Lines [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	285	304
60-89 Days Past Due	292	33
90 Days or More Past Due	150	184
Total Past Due	727	521
Current	26,874	28,585
90-days Past Due and Still Accruing
Non- accrual Loans	150	236
Residential real estate, Single Family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	623	74
60-89 Days Past Due	1,315	29
90 Days or More Past Due	261	1,733
Total Past Due	2,199	1,836
Current	57,250	64,521
90-days Past Due and Still Accruing
Non- accrual Loans	261	1,762
Residential Real Estate, Multifamily [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due
60-89 Days Past Due
90 Days or More Past Due
Total Past Due
Current	5,393	5,785
90-days Past Due and Still Accruing
Non- accrual Loans
Consumer - Non Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due		186
60-89 Days Past Due
90 Days or More Past Due	12
Total Past Due	12	186
Current	1,370	1,836
90-days Past Due and Still Accruing
Non- accrual Loans	$ 12

ALLIANCE BANKSHARES CORP 10-Q