Income Taxes - Schedule of Deferred Tax and Related Valuation Allowance (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Accrued bonus	$ 19,572	$ 14,266
Deferred revenue	9,536us-gaap_DeferredTaxAssetsDeferredIncome	5,691us-gaap_DeferredTaxAssetsDeferredIncome
Deferred rent	10,518akam_DeferredTaxAssetsDeferredRent	6,738akam_DeferredTaxAssetsDeferredRent
Stock-based compensation	27,538	30,125
Net operating losses	11,466	14,392
Tax credit carryforwards	18,066	11,107
Other	7,276us-gaap_DeferredTaxAssetsOther	5,361us-gaap_DeferredTaxAssetsOther
Deferred tax assets	103,972us-gaap_DeferredTaxAssetsGross	87,680us-gaap_DeferredTaxAssetsGross
Depreciation and amortization	(14,868)	(15,607)
Acquired intangible assets	(40,126)	(19,530)
Internal-use software development costs capitalized	(39,396)	(31,970)
Deferred tax liabilities	(94,390)us-gaap_DeferredTaxLiabilities	(67,107)us-gaap_DeferredTaxLiabilities
Valuation allowance	(1,222)	(1,251)
Net deferred tax assets	$ 8,360us-gaap_DeferredTaxAssetsLiabilitiesNet	$ 19,322us-gaap_DeferredTaxAssetsLiabilitiesNet

Deferred Tax Assets, Deferred Rent

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Deferred Tax Liabilities, Depreciation and Amortization

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

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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 after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards, net of deferred tax liability attributable to taxable temporary differences.

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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 other deductible tax carryforwards not separately disclosed.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from compensation and benefits costs.

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

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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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Amount of deferred tax liability attributable to taxable temporary differences net of deferred tax asset attributable to deductible temporary differences and carryforwards after valuation allowances.

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Amount of deferred tax liability attributable to taxable temporary differences from capitalized software.

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Amount of deferred tax liability attributable to taxable temporary differences from intangible assets other than goodwill.

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