14. Regulatory Matters (Detail) - Table of Capital Adequacy Requirements (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
American River Bankshares and Subsidiaries [Member] | Minimum Regulatory Requirment [Member] | Leverage Ratio [Member]
Capital Leverage Ratio (in Dollars)	$ 22,900	$ 22,624
Capital Leverage Ratio	4.00%	4.00%
American River Bankshares and Subsidiaries [Member] | Minimum Regulatory Requirment [Member] | Tier 1 Risk-Based Capital Ratio [Member]
Tier 1 Risk-Based Capital Ratio (in Dollars)	12,297	13,763
Tier 1 Risk-Based Capital Ratio	4.00%	4.00%
American River Bankshares and Subsidiaries [Member] | Minimum Regulatory Requirment [Member] | Total Risk-Based Capital Ratio [Member]
Total Risk-Based Capital Ratio (in Dollars)	24,747	27,743
Total Risk-Based Capital Ratio	8.00%	8.00%
American River Bankshares and Subsidiaries [Member] | Leverage Ratio [Member]
Capital Leverage Ratio (in Dollars)	73,388	74,037
Capital Leverage Ratio	12.80%	13.10%
American River Bankshares and Subsidiaries [Member] | Tier 1 Risk-Based Capital Ratio [Member]
Tier 1 Risk-Based Capital Ratio (in Dollars)	73,388	74,037
Tier 1 Risk-Based Capital Ratio	23.90%	21.50%
American River Bankshares and Subsidiaries [Member] | Total Risk-Based Capital Ratio [Member]
Total Risk-Based Capital Ratio (in Dollars)	77,255	78,372
Total Risk-Based Capital Ratio	25.10%	22.80%
American River Bank [Member] | Minimum Regulatory Requirment [Member] | Leverage Ratio [Member]
Capital Leverage Ratio (in Dollars)	22,880	22,524
Capital Leverage Ratio	4.00%	4.00%
American River Bank [Member] | Minimum Regulatory Requirment [Member] | Tier 1 Risk-Based Capital Ratio [Member]
Tier 1 Risk-Based Capital Ratio (in Dollars)	12,283	13,756
Tier 1 Risk-Based Capital Ratio	4.00%	4.00%
American River Bank [Member] | Minimum Regulatory Requirment [Member] | Total Risk-Based Capital Ratio [Member]
Total Risk-Based Capital Ratio (in Dollars)	24,720	27,729
Total Risk-Based Capital Ratio	8.00%	8.00%
American River Bank [Member] | Well Capitalized Institution [Member] | Leverage Ratio [Member]
Capital Leverage Ratio (in Dollars)	28,600	28,155
Capital Leverage Ratio	5.00%	5.00%
American River Bank [Member] | Well Capitalized Institution [Member] | Tier 1 Risk-Based Capital Ratio [Member]
Tier 1 Risk-Based Capital Ratio (in Dollars)	18,425	20,634
Tier 1 Risk-Based Capital Ratio	6.00%	6.00%
American River Bank [Member] | Well Capitalized Institution [Member] | Total Risk-Based Capital Ratio [Member]
Total Risk-Based Capital Ratio (in Dollars)	30,900	34,661
Total Risk-Based Capital Ratio	10.00%	10.00%
American River Bank [Member] | Leverage Ratio [Member]
Capital Leverage Ratio (in Dollars)	72,284	69,489
Capital Leverage Ratio	12.60%	12.30%
American River Bank [Member] | Tier 1 Risk-Based Capital Ratio [Member]
Tier 1 Risk-Based Capital Ratio (in Dollars)	72,284	69,489
Tier 1 Risk-Based Capital Ratio	23.50%	20.20%
American River Bank [Member] | Total Risk-Based Capital Ratio [Member]
Total Risk-Based Capital Ratio (in Dollars)	$ 76,146	$ 73,822
Total Risk-Based Capital Ratio	24.80%	21.50%