Basis Of Presentation (Policy)	6 Months Ended
Basis Of Presentation (Policy)	Jun. 30, 2012
Accounting Policies [Abstract]
Use Of Estimates	Use of Estimates The preparation of consolidated financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the financial statements, including judgments about investment classifications, and the reported amounts of net revenue and expenses during the reporting period. On an ongoing basis, management evaluates its estimates based on historical experience and on various other factors that the Company believes to be reasonable under the circumstances. Actual results could differ from those estimates. In the first quarter of 2011, the Company made a change in estimate regarding the remaining service obligations to its annual eFax® subscribers. As a result of system upgrades, the Company is now basing the estimate on the actual remaining service obligations to these customers. Due to this change, the Company recorded a one-time, non-cash increase to deferred revenues of $10.3 million with an equal offset to revenues. This change in estimate reduced net income by approximately $7.6 million, net of tax, and reduced basic and diluted earnings per share for the six months ended June 30, 2011 by $0.17 and $0.16, respectively.
Allowances For Doubtful Accounts	Allowances for Doubtful Accounts j2 Global reserves for receivables it may not be able to collect. These reserves are typically driven by the volume of credit card declines and past due invoices and are based on historical experience as well as an evaluation of current market conditions. On an ongoing basis, management evaluates the adequacy of these reserves.
Revenue Recognition	Revenue Recognition The Company’s subscriber revenues substantially consist of monthly recurring subscription and usage-based fees, which are primarily paid in advance by credit card. In accordance with GAAP, the Company defers the portions of monthly, quarterly, semi-annually and annually recurring subscription and usage-based fees collected in advance and recognizes them in the period earned. Additionally, the Company defers and recognizes subscriber activation fees and related direct incremental costs over a subscriber’s estimated useful life. The Company’s patent revenues (included in “other revenues”) consist of patent license revenues generated under license agreements that provide for the payment of contractually determined fully paid-up or royalty-bearing license fees to j2 Global in exchange for the grant of non-exclusive, retroactive and future licenses to the Company’s patented technology. Patent revenues also consist of revenues generated from the sale of patents. Patent license revenues are recognized when earned over the term of the license agreements. With regard to fully paid-up license arrangements, the Company generally recognizes as revenue in the period the agreement is executed the portion of the payment attributable to past use of the patented technology and amortizes the remaining portion of such payments on a straight line basis over the life of the licensed patent(s). With regard to royalty-bearing license arrangements, j2 Global recognizes revenues of license fees earned during the applicable period. With regard to patent sales, the Company recognizes as revenue in the period of the sale the portion of the purchase price over the carrying value of the patent(s) sold. j2 Global also recognizes other licensing revenues (included in “other revenues”) that primarily consist of revenues generated under license agreements for certain technology to third parties. Other licensing revenues are recognized when earned in accordance with the terms of the agreement. Generally, revenue is recognized as the third party uses the licensed technology over the period. The Company’s advertising revenues (included in “other revenues”) primarily consist of revenues derived by delivering email messages to its customers on behalf of advertisers. Revenues are recognized in the period in which the advertising services are performed, provided that no significant j2 Global obligations remain and the collection of the resulting receivable is reasonably assured.
Fair Value Measurements	Fair Value Measurements j2 Global complies with the provisions of Financial Accounting Standards Board (“FASB”) ASC Topic No. 820, Fair Value Measurements and Disclosures (“ASC 820”), in measuring fair value and in disclosing fair value measurements. ASC 820 provides a framework for measuring fair value and expands the disclosures required for fair value measurements of financial and non-financial assets and liabilities. As of June 30, 2012 and December 31, 2011, the carrying value of cash and cash equivalents, short-term investments, accounts receivable, interest receivable, accounts payable, accrued expenses, interest payable and customer deposits approximated fair value due to the short-term nature of such instruments. As of the same dates, the carrying value of other long-term liabilities approximated fair value as the related interest rates approximate rates currently available to j2 Global.
Debt, Policy [Policy Text Block]	Debt Issuance Costs j2 Global capitalized costs incurred in connection with borrowings and issuance of debt securities. These costs are amortized and included in interest expense over the life of the borrowing or term of the credit facility using the interest method.
Concentration Of Credit Risk	Concentration of Credit Risk All of the Company’s cash, cash equivalents and marketable securities are invested at major financial institutions primarily within the United States, United Kingdom and Ireland. These institutions are required to invest the Company’s cash in accordance with the Company’s investment policy with the principal objectives being preservation of capital, fulfillment of liquidity needs and above market returns commensurate with preservation of capital. The Company’s investment policy also requires that investments in marketable securities be in only highly rated instruments, with limitations on investing in securities of any single issuer. However, these investments are not insured against the possibility of a total or near complete loss of earnings or principal and are inherently subject to the credit risk related to the continued credit worthiness of the underlying issuer and general credit market risks. At June 30, 2012 and December 31, 2011, the Company’s cash and cash equivalents were maintained in accounts that are insured up to the limit determined by the applicable governmental agency. The amount held in Ireland by some of our banks are fully insured through December 31, 2012 (subject to European Union state aid approval); however, the insured amount held in other institutions is immaterial in comparison to the total amount of the Company’s cash and cash equivalents held by these institutions which is not insured. These institutions are primarily in the United States, however, the Company does have accounts within several other countries including Australia, Austria, China, France, Germany, Italy, Japan, Malaysia, the Netherlands, Poland and the United Kingdom.
Income Taxes	Income Taxes The Company must make certain estimates and judgments in determining income tax expense for financial statement purposes. These estimates and judgments occur in the following areas, among others: (i) calculation of tax credits, benefits and deductions; (ii) calculation of tax assets and liabilities arising from differences in the timing of recognition of revenue and expense for tax and financial statement purposes; and (iii) interest and penalties related to uncertain tax positions. Significant changes to these estimates may result in an increase or decrease to the Company’s tax provision in the current or a subsequent period. The Company must assess the likelihood that it will be able to recover its deferred tax assets. If recovery is not likely, the Company must increase its provision for taxes by recording a valuation allowance against the deferred tax assets that the Company estimates will not ultimately be recoverable. The Company believes that it will ultimately recover a substantial majority of the deferred tax assets recorded on its consolidated condensed balance sheets. However, should there be a change in the Company’s ability to recover its deferred tax assets, the Company’s tax provision would increase in the period in which j2 Global determined that the recovery was not likely. The calculation of the Company’s tax liabilities involves dealing with uncertainties in the application of complex tax laws. j2 Global recognizes liabilities for uncertain tax positions based on a two-step process. The first step is to evaluate the tax position for recognition by determining if the weight of available evidence indicates that it is more likely than not that the position will be sustained on audit, including resolution of related appeals or litigation processes, if any. If the Company determines that a tax position will more likely than not be sustained on audit, then the second step requires j2 Global to estimate and measure the tax benefit as the largest amount that is more than 50% likely to be realized upon ultimate settlement. It is inherently difficult and subjective to estimate such amounts, as j2 Global has to determine the probability of various possible outcomes. j2 Global reevaluates these uncertain tax positions on a quarterly basis. This evaluation is based on factors including, but not limited to, changes in facts or circumstances, changes in tax law, effectively settled issues under audit and new audit activity. Such a change in recognition or measurement would result in the recognition of a tax benefit or an additional charge to the tax provision.
Comparability of Prior Year Financial Data, Policy [Policy Text Block]	Reclassifications Certain prior year reported amounts have been reclassified to conform with the 2012 presentation.

Disclosure of accounting policy for income taxes, which may include its accounting policies for recognizing and measuring deferred tax assets and liabilities and related valuation allowances, recognizing investment tax credits, operating loss carryforwards, tax credit carryforwards, and other carryforwards, methodologies for determining its effective income tax rate and the characterization of interest and penalties in the financial statements.

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Name Statement of Financial Accounting Standard (FAS)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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+ Details

- Definition

Describes how an entity determines the level of its allowance for doubtful accounts for its trade and other accounts receivable balances, and when impairments, charge-offs or recoveries are recognized. The description identifies the factors that influence management's establishment of the level of the allowance (for example, historical losses and existing economic conditions) and may also include discussion of the risk elements relevant to particular categories of receivables.

+ References+ Details

- Definition

Disclosure of accounting policy for revenue recognition. If the entity has different policies for different types of revenue transactions, the policy for each material type of transaction is generally disclosed. If a sales transaction has multiple element arrangements (for example, delivery of multiple products, services or the rights to use assets) the disclosure may indicate the accounting policy for each unit of accounting as well as how units of accounting are determined and valued. The disclosure may encompass important judgment as to appropriateness of principles related to recognition of revenue. The disclosure also may indicate the entity's treatment of any unearned or deferred revenue that arises from the transaction.

+ References+ Details

- Definition

Disclosure of accounting policy for the use of estimates in the preparation of financial statements in conformity with generally accepted accounting principles.

+ References+ Details