Weighted Average Exercise Prices for Options Granted and Exercisable and Weighted Average Remaining Contractual Life for Options Outstanding (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Outstanding	724,904	561,029	705,345	1,388,514
Weighted Average Exercise Price, Outstanding	$ 9.22	$ 7.76	$ 7.70	$ 7.44
Weighted Average Exercisable, Exercise Price	$ 7.82	$ 7.70	$ 7.95	$ 7.26
Incentive Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Outstanding	724,904	561,029
Number of Shares, Expected to Vest	713,172	560,972
Number of Shares, Exercisable	447,879	554,362
Weighted Average Exercise Price, Outstanding	$ 9.22	$ 7.76
Weighted Average Exercise Price, Expected to Vest	$ 9.19	$ 7.76
Weighted Average Exercisable, Exercise Price	$ 7.82	$ 7.70
Weighted Average Remaining Life, Outstanding	90 months	83 months
Weighted Average Remaining Contractual Life, Expected to Vest	89 months	83 months
Weighted Average Remaining Contractual Life, Exercisable	71 months	83 months
Intrinsic Value, Outstanding	$ 1,774	$ 9,276
Intrinsic Value, Expected to Vest	1,773	9,275
Intrinsic Value, Exercisable	1,738	9,196
Performance Based Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Outstanding	107,689
Number of Shares, Expected to Vest	107,689
Weighted Average Exercise Price, Outstanding	$ 11.49
Weighted Average Exercise Price, Expected to Vest	$ 11.49
Weighted Average Remaining Life, Outstanding	36 months
Weighted Average Remaining Contractual Life, Expected to Vest	36 months
Weighted Average Remaining Contractual Life, Exercisable	0 months
Intrinsic Value, Outstanding	14
Intrinsic Value, Expected to Vest	$ 14

Weighted Average Exercise Prices for Options Granted and Exercisable and Weighted Average Remaining Contractual Life for Options Outstanding (Detail) (USD $)
In Thousands, except Share data, unless otherwise specified

12 Months Ended

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of Shares, Outstanding

724,904us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber

561,029us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber

705,345us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber

1,388,514us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber

Weighted Average Exercise Price, Outstanding

$ 9.22us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice

$ 7.76us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice

$ 7.70us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice

$ 7.44us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice

Weighted Average Exercisable, Exercise Price

$ 7.82us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice

$ 7.70us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice

$ 7.95us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice

$ 7.26us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice

Incentive Stock Option Plan

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of Shares, Outstanding

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561,029us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
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Number of Shares, Expected to Vest

713,172us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber
/ us-gaap_PlanNameAxis
= avd_IncentiveStockOptionPlanMember

560,972us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber
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= avd_IncentiveStockOptionPlanMember

Number of Shares, Exercisable

447,879us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
/ us-gaap_PlanNameAxis
= avd_IncentiveStockOptionPlanMember

554,362us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
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= avd_IncentiveStockOptionPlanMember

Weighted Average Exercise Price, Outstanding

$ 9.22us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
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$ 7.76us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
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Weighted Average Exercise Price, Expected to Vest

$ 9.19us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= avd_IncentiveStockOptionPlanMember

$ 7.76us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice
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= avd_IncentiveStockOptionPlanMember

Weighted Average Exercisable, Exercise Price

$ 7.82us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= avd_IncentiveStockOptionPlanMember

$ 7.70us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= avd_IncentiveStockOptionPlanMember

Weighted Average Remaining Life, Outstanding

90 months

83 months

Weighted Average Remaining Contractual Life, Expected to Vest

89 months

83 months

Weighted Average Remaining Contractual Life, Exercisable

71 months

83 months

Intrinsic Value, Outstanding

$ 1,774us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue
/ us-gaap_PlanNameAxis
= avd_IncentiveStockOptionPlanMember

$ 9,276us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue
/ us-gaap_PlanNameAxis
= avd_IncentiveStockOptionPlanMember

Intrinsic Value, Expected to Vest

1,773us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue
/ us-gaap_PlanNameAxis
= avd_IncentiveStockOptionPlanMember

9,275us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue
/ us-gaap_PlanNameAxis
= avd_IncentiveStockOptionPlanMember

Intrinsic Value, Exercisable

1,738us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1
/ us-gaap_PlanNameAxis
= avd_IncentiveStockOptionPlanMember

9,196us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1
/ us-gaap_PlanNameAxis
= avd_IncentiveStockOptionPlanMember

Performance Based Options

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of Shares, Outstanding

107,689us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
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= avd_PerformanceBasedOptionsMember

Number of Shares, Expected to Vest

107,689us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber
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= avd_PerformanceBasedOptionsMember

Weighted Average Exercise Price, Outstanding

$ 11.49us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
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= avd_PerformanceBasedOptionsMember

Weighted Average Exercise Price, Expected to Vest

$ 11.49us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice
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= avd_PerformanceBasedOptionsMember

Weighted Average Remaining Life, Outstanding

36 months

Weighted Average Remaining Contractual Life, Expected to Vest

36 months

Weighted Average Remaining Contractual Life, Exercisable

0 months

Intrinsic Value, Outstanding

14us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue
/ us-gaap_PlanNameAxis
= avd_PerformanceBasedOptionsMember

Intrinsic Value, Expected to Vest

$ 14us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue
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= avd_PerformanceBasedOptionsMember

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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- Definition

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

+ References

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-Name Accounting Standards Codification

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-SubTopic 10

-Section 50

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of fully vested and expected to vest options outstanding.

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As of the balance sheet date, the number of shares into which fully vested and expected to vest stock options outstanding can be converted under the option plan.

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As of the balance sheet date, the weighted-average exercise price for outstanding stock options that are fully vested or expected to vest.

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Weighted average remaining contractual term for fully vested and expected to vest options outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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