Income Taxes - Deferred Tax Assets and Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Deferred tax assets:
Net operating loss carryforwards	$ 315,773	$ 294,910
Research and development credit carryforwards	81,546	79,839
Inventory write-downs and other reserves	7,642	8,068
Capitalization of research and development costs	6,245	5,915
Goodwill	3,147amcc_DeferredTaxAssetsGoodwill	4,007amcc_DeferredTaxAssetsGoodwill
Intangible assets	26,031amcc_DeferredTaxAssetsIntangibleAssets	32,290amcc_DeferredTaxAssetsIntangibleAssets
Investment impairment	3,982	3,494
Stock-based compensation	28,921	26,664
Depreciation and amortization	1,903	3,253
Other	970us-gaap_DeferredTaxAssetsOther	1,182us-gaap_DeferredTaxAssetsOther
Total deferred tax assets	476,160us-gaap_DeferredTaxAssetsGross	459,622us-gaap_DeferredTaxAssetsGross
Valuation allowance	(475,545)	(459,081)
Total deferred tax benefit	$ 615us-gaap_DeferredTaxAssetsLiabilitiesNet	$ 541us-gaap_DeferredTaxAssetsLiabilitiesNet

Deferred Tax Assets, Depreciation and Amortization

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from goodwill.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from intangible assets.

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Deferred Tax Assets, Tax Deferred Expense, Inventory Impairment and Other Reserves

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from in-process research and development costs expensed in connection with a business combination.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences not separately disclosed.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible research tax credit carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from share-based compensation.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from estimated impairment losses.

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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