Income Taxes Income Taxes (Deferred Tax Assets And Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Abstract]
Deferred Tax Assets, Operating Loss Carryforwards	$ 13,774	$ 9,596
Deferred Tax Assets, Tax Credit Carryforwards	14,091	9,233
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Accrued Liabilities	7,114	1,196
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Allowance for Doubtful Accounts	1,132	1,423
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost	3,632	4,917
Deferred Tax Assets, Property, Plant and Equipment	0	1,266
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Impairment Losses	76	161
Deferred Tax Assets, Gain On Sale Of Intangible Assets	0	123
Deferred Tax Assets, Deferred Income	250us-gaap_DeferredTaxAssetsDeferredIncome	812us-gaap_DeferredTaxAssetsDeferredIncome
Deferred Tax Assets, State Taxes	2,333us-gaap_DeferredTaxAssetsStateTaxes	1,451us-gaap_DeferredTaxAssetsStateTaxes
Deferred Tax Assets, Other	789us-gaap_DeferredTaxAssetsOther		0us-gaap_DeferredTaxAssetsOther
Deferred Tax Assets, Gross	43,191us-gaap_DeferredTaxAssetsGross	30,178us-gaap_DeferredTaxAssetsGross
Deferred Tax Assets, Valuation Allowance	(11,358)	(8,493)
Deferred Tax Assets, Net of Valuation Allowance	31,833us-gaap_DeferredTaxAssetsNet	21,685us-gaap_DeferredTaxAssetsNet
Deferred Tax Liabilities, Property, Plant and Equipment	(5,883)	0
Deferred Tax Liabilities, Intangible Assets	(51,566)	(47,711)
Deferred Tax Liabilities, Prepaid Insurance	(420)	(369)
Deferred Tax Liability, Convertible Debt	(26,272)	0
Deferred Tax Liabilities, Foreign Other	(7,981)jcom_DeferredTaxLiabilitiesForeignOther	(6,359)jcom_DeferredTaxLiabilitiesForeignOther
Deferred Tax Liabilities, Net	(92,122)us-gaap_DeferredTaxLiabilities	(54,439)us-gaap_DeferredTaxLiabilities
Deferred Tax Assets, Net	$ (60,289)us-gaap_DeferredTaxAssetsLiabilitiesNet	$ (32,754)us-gaap_DeferredTaxAssetsLiabilitiesNet

Deferred tax assets, gain on sale of intangible assets.

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Deferred tax liabilities, foreign other.

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Deferred tax liabilities, prepaid insurance.

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Deferred Tax Liability, Convertible Debt

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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 after 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 operating loss carryforwards.

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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 temporary differences from property, plant, and equipment.

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

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The tax effect as of the balance sheet date of the amount of future tax deductions arising from all unused tax credit carryforwards which have been reduced by a valuation allowance.

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-Glossary 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 accrued liabilities.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from the allowance for doubtful accounts.

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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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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 intangible assets other than goodwill.

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Amount of deferred tax liability attributable to taxable temporary differences from property, plant, and equipment.

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