Basis Of Presentation (Policy)	9 Months Ended
Basis Of Presentation (Policy)	Sep. 30, 2015
Accounting Policies [Abstract]
Use Of Estimates	Use of Estimates The preparation of consolidated financial statements in accordance with accounting principles generally accepted in the United States of America ("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. We believe that our most significant estimates are those related to valuation and impairment of marketable securities, valuation of assets acquired and liabilities assumed in connection with business combinations, long-lived and intangible asset impairment, contingent consideration, income taxes, contingencies and allowances for doubtful accounts. 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 materially differ from those estimates.
Allowances For Doubtful Accounts	Allowances for Doubtful Accounts j2 Global reserves for receivables it may not be able to collect. The reserves for the Company's Business Cloud Services segment are typically driven by the historical volume of credit card declines, an evaluation of current market conditions and past due invoices based on historical experience. The reserves for the Company's Digital Media segment are typically driven by past due invoices based on historical experience. Management evaluates the adequacy of these reserves on an ongoing basis.
Revenue Recognition	Revenue Recognition Business Cloud Services The Company's Business Cloud Services 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 recognizes revenue when persuasive evidence of an arrangement exists, services have been provided, the sales price is fixed and determinable and collection is probable. 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. j2 Global's Business Cloud Services also include 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 our intellectual property, including patented technology. Patent revenues may 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 recognizes as revenue in the period the license agreement is executed the portion of the payment attributable to past use of the intellectual property and amortizes the remaining portion of such payments on a straight-line basis, or pro-rata revenue basis, as appropriate over the life of the licensed patent(s). With regard to royalty-bearing license arrangements, the Company 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 amount of the purchase price over the carrying value of the patent(s) sold. The Business Cloud Services business also generates revenues by licensing certain technology to third parties. These licensing revenues are recognized when earned in accordance with the terms of the underlying agreement. Generally, revenue is recognized as the third party uses the licensed technology over the period. Digital Media The Company's Digital Media revenues primarily consist of revenues generated from the sale of advertising campaigns that are targeted to the Company's proprietary websites and to those websites operated by third parties that are part of the Digital Media business's advertising network. Revenues for these advertising campaigns are recognized as earned either when an ad is placed for viewing by a visitor to the appropriate web page or when the visitor "clicks through" on the ad, depending upon the terms with the individual advertiser. Revenues for Digital Media business-to-business operations consist of lead-generation campaigns for IT vendors and are recognized as earned when the Company delivers the qualified leads to the customer. j2 Global also generates Digital Media revenues through the license of certain assets to clients, for the clients' use in their own promotional materials or otherwise. Such assets may include logos, editorial reviews, or other copyrighted material. Revenues under such license agreements are recognized when the assets are delivered to the client. Also, Digital Media revenues are generated through the license of certain speed testing technology which is recognized when delivered to the client through providing data services primarily to Internet Service Providers ("ISPs") and wireless carriers which is recognized as earned over the term of the access period. The Digital Media business also generates other types of revenues, including business listing fees, subscriptions to online publications, and from other sources. Such other revenues are recognized as earned. The Company determines whether Digital Media revenue should be reported on a gross or net basis by assessing whether the Company is acting as the principal or agent in the transaction. If the Company is acting as the principal in a transaction, the Company reports revenue on a gross basis. If the Company is acting as an agent in a transaction, the Company reports revenue on a net basis. In determining whether the Company acts as the principal or an agent, the Company follows the accounting guidance for principal-agent considerations and the Company places the most weight on three factors: whether or not the Company (i) is the primary obligor in the arrangement, (ii) has latitude in determining pricing and (iii) bears credit risk. The Company records revenue on a gross basis with respect to revenue generated (i) by the Company serving online display and video advertising across its owned-and-operated web properties, on third party sites or on unaffiliated advertising networks, (ii) through the Company's lead-generation business and (iii) through the Company's Digital Media licensing program. The Company records revenue on a net basis with respect to revenue paid to the Company by certain third-party advertising networks who serve online display and video advertising across the Company's owned-and-operated web properties or certain third party sites.
Fair Value Measurements	Fair Value Measurements As of September 30, 2015 and December 31, 2014, the carrying value of cash and cash equivalents, short-term investments, accounts receivable, interest receivable, accounts payable, accrued expenses, interest payable, customer deposits and long-term debt are reflected in the financial statements at cost. With the exception of long-term debt, cost approximates fair value due to the short-term nature of such instruments. The fair value of the Company's senior unsecured notes was determined using the quoted market prices of debt instruments with similar terms and maturities, if available. 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 and Debt Discount j2 Global capitalizes costs incurred with borrowing and issuance of debt securities and records debt discounts as a reduction to the debt amount. j2 Global capitalized third-party costs incurred in connection with its sale of senior unsecured notes within long-term other assets and recorded the original purchase discount as a reduction to such notes (See Note 7 - Long Term Debt). These costs and discounts are amortized and included in interest expense over the life of the borrowing or term of the credit facility using the effective interest method.
Concentration Of Credit Risk	Concentration of Credit Risk All of the Company’s cash, cash equivalents and marketable securities are invested primarily at major financial institutions within the United States, United Kingdom and Ireland, with cash and cash equivalents also held at financial institutions within several other countries, including Australia, Austria, Canada, China, France, Germany, Italy, Japan, New Zealand, the Netherlands and Poland. 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 September 30, 2015 and December 31, 2014, 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 Company's deposits held in qualifying financial institutions in Ireland are fully insured through March 28, 2018 to the extent on deposit prior to March 28, 2013. With respect to the Company's deposits with financial institutions in other jurisdictions, the insured amounts are immaterial in comparison to the total amount of the Company’s cash and cash equivalents held by these institutions which is not insured.
Business Combinations Policy [Policy Text Block]	Contingent Consideration j2 Global measures contingent earn-out liabilities in connection with acquisitions at fair value on a recurring basis using significant unobservable inputs and such liabilities are classified within Level 3 of the fair value hierarchy (see Note 5 - Fair Value Measurements). The Company may use various valuation techniques depending on the terms and conditions of the contingent consideration including a Monte-Carlo simulation. This simulation uses a probability distribution for each significant input to produce hundreds or thousands of possible outcomes and the results are analyzed to determine probabilities of different outcomes occurring. Significant increases or decreases to these inputs in isolation would result in a significantly higher or lower liability with a higher liability capped by the contractual maximum of the contingent earn-out obligation, if any. Ultimately, the liability will be equivalent to the amount paid, and the difference between the fair value estimate and the amount paid will be recorded in earnings. If the amount paid is less than the liability on the acquisition date, such deficiency is reflected as cash used in financing activities in our consolidated statements of cash flows. Any amount paid in excess of the liability on the acquisition date is reflected as cash used in operating activities. j2 Global reviews and re-assess the estimated fair value of contingent consideration on a quarterly basis, and the updated fair value could be materially different from the initial estimates or prior quarterly amounts. Changes in the estimated fair value of our contingent earn-out liabilities are reported in operating income, except for the time component of the present value calculation which is reported in interest expense.
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 condensed consolidated 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 as a result of recording any necessary valuation allowances, 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.
Earnings Per Share, Policy [Policy Text Block]	Earnings Per Common Share Earnings per common share ("EPS") is calculated pursuant to the two-class method as defined in ASC Topic No. 260, Earnings per Share (“ASC 260”), which specifies that all outstanding unvested share-based payment awards that contain rights to nonforfeitable dividends or dividend equivalents are considered participating securities and should be included in the computation of EPS pursuant to the two-class method. Basic EPS is calculated by dividing net distributed and undistributed earnings allocated to common shareholders, excluding participating securities and the net income attributable to noncontrolling interest, by the weighted-average number of common shares outstanding. The Company's participating securities consist of its unvested share-based awards that contain rights to nonforfeitable dividends or dividend equivalents.