Basis Of Presentation (Policy)	6 Months Ended
Basis Of Presentation (Policy)	Jun. 30, 2017
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 the valuation of assets acquired and liabilities assumed in connection with business combinations, long-lived and intangible asset impairment, contingent consideration, income taxes and 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. These reserves for the Company’s Business Cloud Services segment 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. These reserves for the Company’s Digital Media segment are typically driven by past due invoices based on historical experience. On an ongoing basis, management evaluates the adequacy of these reserves.
Revenue Recognition, Policy [Policy Text Block]	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. Along with our numerous proprietary Business Cloud Services solutions, the Company also generates revenues by reselling various third party solutions, primarily through our email security and online backup lines of business. These third party solutions, along with our proprietary products, allow the Company to offer customers a variety of solutions to better meet their needs. The Company determines whether reseller revenue should be reported on a gross or net basis by assessing whether the Company is acting as the principal or an 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 reseller revenue as the Company is the primary obligator in the arrangement, has latitude in determining pricing and bears all credit risk associated with our reseller program partners. 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 an 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 and certain third party sites.
Fair Value of Financial Instruments, Policy [Policy Text Block]	Fair Value Measurements j2 Global complies with the provisions of Financial Accounting Standards Board (“FASB”) Accounting Standard Codification (“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, 2017, 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 outstanding debt 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.
Property, Plant and Equipment, Policy [Policy Text Block]	Property and Equipment Property and equipment are stated at cost. Equipment under capital leases is stated at the present value of the minimum lease payments. Depreciation is calculated using the straight-line method over the estimated useful lives of the assets. The estimated useful lives of property and equipment range from 1 to 10 years. Fixtures, which are comprised primarily of leasehold improvements and equipment under capital leases, are amortized on a straight-line basis over their estimated useful lives or for leasehold improvements, the related lease term, if less. The Company has capitalized certain internal use software and website development costs which are included in property and equipment. The estimated useful life of costs capitalized is evaluated for each specific project and ranges from 1 to 5 years.
Debt	Debt Issuance Costs and Debt Discount j2 Global capitalizes costs incurred with borrowing and issuance of debt securities and records debt issuance costs and discounts as a reduction to the debt amount. 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.
Business Combinations Policy [Policy Text Block]	Contingent Consideration j2 Global measures the contingent earn-out liabilities in connection with acquisitions at fair value on a recurring basis using significant unobservable inputs 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. 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. The amount paid that is less than or equal to the liability on the acquisition date 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.
Segment Reporting	Segment Reporting Accounting guidance establishes standards for the way that public business enterprises report information about operating segments in their annual consolidated financial statements and requires that those enterprises report selected information about operating segments in interim financial reports. Accounting guidance also establishes standards for related disclosures about products and services, geographic areas and major customers. The Company operates as two segments: (1) Business Cloud Services and (2) Digital Media.
Comparability of Prior Year Financial Data	Reclassifications Certain prior year reported amounts have been reclassified to conform to the 2017 presentation.