Condensed Consolidating Financials Condensed Statement of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 37,375	$ 28,759	$ 98,169	$ 92,573
Depreciation and amortization			63,635	43,307
Accretion (Amortization) of Discounts and Premiums, Investments			871	983
Amortization of financing costs and discounts			6,774	2,828
Share-based Compensation			8,943	6,538
Excess Tax Benefit from Share-based Compensation, Operating Activities			(4,541)	(6,728)
Provision for doubtful accounts			5,015	3,278
Deferred income taxes			219	(2,954)
(Gain) loss on sale of available-for-sale investments			37	69
Decrease (increase) in:
Increase (Decrease) in Accounts Receivable			(4,296)	1,267
Increase (Decrease) in Prepaid Expense and Other Assets			2,815	(4,124)
Increase (Decrease) in Other Operating Assets			(77)	(128)
(Decrease) increase in:
Accounts payable and accrued expenses			(5,783)	(2,949)
Income taxes payable			(13,565)	7,565
Deferred revenue			(3,727)	(815)
Liability for uncertain tax positions			(9,916)	(8,071)
Other			4,074	(380)
Net Cash Provided by (Used in) Operating Activities			148,573	132,121
Cash flows from investing activities:
Maturity of certificates of deposit			65	14,520
Purchase of certificates of deposit			(62)	0
Sales of available-for-sale investments			87,976	60,456
Payments to Acquire Available-for-sale Securities			(78,281)	(112,983)
Payments to Acquire Property, Plant, and Equipment			(11,927)	(7,755)
Proceeds from sale of assets			0	608
Payments to Acquire Businesses, Net of Cash Acquired			(259,838)	(118,238)
Payments to Acquire Intangible Assets			(1,258)	(4,806)
Payments to Acquire Interest in Subsidiaries and Affiliates			0	0
Intercompany Investing Activities			0
Net Cash Provided by (Used in) Investing Activities			(263,325)	(168,198)
Cash flows from financing activities:
Payments for Repurchase of Common Stock			(3,159)	(5,473)
Issuance of common stock under employee stock purchase plan			196	199
Exercise of stock options			4,618	6,387
Payments of Dividends			(43,526)	(38,547)
Excess tax benefits from share-based compensation			4,541	6,728
Deferred payments for acquisitions			(5,411)	(14,316)
Proceeds from (Payments for) Other Financing Activities			(250)	(711)
Payments of Distributions to Affiliates			0	0
Net Cash Provided by (Used in) Financing Activities			(42,991)	345,240
Effect of exchange rate changes on cash and cash equivalents			(3,552)	(1,967)
Cash and Cash Equivalents, Period Increase (Decrease)			(161,295)	307,196
Cash and cash equivalents	272,368	514,997	272,368	514,997	$ 433,663	$ 207,801
Proceeds from Issuance of Long-term Debt			0	402,500
Payments of Debt Issuance Costs			0	(11,527)
j2 Global, Inc. [Member]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	37,375	28,759	98,169	92,573
(Decrease) increase in:
Net Cash Provided by (Used in) Operating Activities			(21,341)	11,254
Cash flows from investing activities:
Maturity of certificates of deposit			65	0
Purchase of certificates of deposit			(62)
Sales of available-for-sale investments			87,976	2,005
Payments to Acquire Available-for-sale Securities			(78,281)	(58,591)
Payments to Acquire Property, Plant, and Equipment			0	0
Proceeds from sale of assets				0
Payments to Acquire Businesses, Net of Cash Acquired			0	0
Payments to Acquire Intangible Assets			0	0
Payments to Acquire Interest in Subsidiaries and Affiliates			0	0
Intercompany Investing Activities			(53,317)
Net Cash Provided by (Used in) Investing Activities			(43,619)	(56,586)
Cash flows from financing activities:
Payments for Repurchase of Common Stock			(3,159)	(739)
Issuance of common stock under employee stock purchase plan			196	76
Exercise of stock options			4,618	1,193
Payments of Dividends			(43,526)	(13,267)
Excess tax benefits from share-based compensation			4,541	1,925
Deferred payments for acquisitions			0	0
Proceeds from (Payments for) Other Financing Activities			0	0
Payments of Distributions to Affiliates			13,713	20,620
Net Cash Provided by (Used in) Financing Activities			(51,043)	358,999
Effect of exchange rate changes on cash and cash equivalents			(1,233)	0
Cash and Cash Equivalents, Period Increase (Decrease)			(117,236)	313,667
Cash and cash equivalents	109,554	313,667	109,554	313,667	226,790	0
Proceeds from Issuance of Long-term Debt				402,500
Payments of Debt Issuance Costs				(12,069)
j2 Cloud Services, Inc. [Member]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	41,260	33,798	113,042	98,283
(Decrease) increase in:
Net Cash Provided by (Used in) Operating Activities			34,297	38,535
Cash flows from investing activities:
Maturity of certificates of deposit			0	8,210
Purchase of certificates of deposit			0
Sales of available-for-sale investments			0	46,863
Payments to Acquire Available-for-sale Securities			0	(54,393)
Payments to Acquire Property, Plant, and Equipment			(1,355)	(925)
Proceeds from sale of assets				0
Payments to Acquire Businesses, Net of Cash Acquired			47	0
Payments to Acquire Intangible Assets			166	(2,871)
Payments to Acquire Interest in Subsidiaries and Affiliates			0	(23,822)
Intercompany Investing Activities			53,317
Net Cash Provided by (Used in) Investing Activities			52,175	(26,938)
Cash flows from financing activities:
Payments for Repurchase of Common Stock			0	(4,734)
Issuance of common stock under employee stock purchase plan			0	123
Exercise of stock options			0	5,194
Payments of Dividends			0	(25,302)
Excess tax benefits from share-based compensation			0	4,803
Deferred payments for acquisitions			0	0
Proceeds from (Payments for) Other Financing Activities			0	0
Payments of Distributions to Affiliates			103,533	11,292
Net Cash Provided by (Used in) Financing Activities			(103,533)	(31,208)
Effect of exchange rate changes on cash and cash equivalents			(7,895)	4
Cash and Cash Equivalents, Period Increase (Decrease)			(24,956)	(19,607)
Cash and cash equivalents	11,854	14,799	11,854	14,799	36,810	34,406
Proceeds from Issuance of Long-term Debt				0
Payments of Debt Issuance Costs				0
Non-Guarantor Subsidiaries [Member]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	41,357	5,492	91,640	46,211
(Decrease) increase in:
Net Cash Provided by (Used in) Operating Activities			135,617	82,332
Cash flows from investing activities:
Maturity of certificates of deposit			0	6,310
Purchase of certificates of deposit			0
Sales of available-for-sale investments			0	11,588
Payments to Acquire Available-for-sale Securities			0	1
Payments to Acquire Property, Plant, and Equipment			(10,572)	(6,830)
Proceeds from sale of assets				608
Payments to Acquire Businesses, Net of Cash Acquired			(259,885)	(118,238)
Payments to Acquire Intangible Assets			(1,424)	(1,935)
Payments to Acquire Interest in Subsidiaries and Affiliates			0	0
Intercompany Investing Activities			0
Net Cash Provided by (Used in) Investing Activities			(271,881)	(108,496)
Cash flows from financing activities:
Payments for Repurchase of Common Stock			0	0
Issuance of common stock under employee stock purchase plan			0	0
Exercise of stock options			0	0
Payments of Dividends			0	22
Excess tax benefits from share-based compensation			0	0
Deferred payments for acquisitions			(5,411)	(14,316)
Proceeds from (Payments for) Other Financing Activities			(250)	(711)
Payments of Distributions to Affiliates			(117,246)	(55,734)
Net Cash Provided by (Used in) Financing Activities			111,585	41,271
Effect of exchange rate changes on cash and cash equivalents			5,576	(1,971)
Cash and Cash Equivalents, Period Increase (Decrease)			(19,103)	13,136
Cash and cash equivalents	150,960	186,531	150,960	186,531	170,063	173,395
Proceeds from Issuance of Long-term Debt				0
Payments of Debt Issuance Costs				542
Consolidation, Eliminations [Member]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(82,617)	(39,290)	(204,682)	(144,494)
(Decrease) increase in:
Net Cash Provided by (Used in) Operating Activities			0	0
Cash flows from investing activities:
Maturity of certificates of deposit			0	0
Purchase of certificates of deposit			0
Sales of available-for-sale investments			0	0
Payments to Acquire Available-for-sale Securities			0	0
Payments to Acquire Property, Plant, and Equipment			0	0
Proceeds from sale of assets				0
Payments to Acquire Businesses, Net of Cash Acquired			0	0
Payments to Acquire Intangible Assets			0	0
Payments to Acquire Interest in Subsidiaries and Affiliates			0	23,822
Intercompany Investing Activities			0
Net Cash Provided by (Used in) Investing Activities			0	23,822
Cash flows from financing activities:
Payments for Repurchase of Common Stock			0	0
Issuance of common stock under employee stock purchase plan			0	0
Exercise of stock options			0	0
Payments of Dividends			0	0
Excess tax benefits from share-based compensation			0	0
Deferred payments for acquisitions			0	0
Proceeds from (Payments for) Other Financing Activities			0	0
Payments of Distributions to Affiliates			0	23,822
Net Cash Provided by (Used in) Financing Activities			0	(23,822)
Effect of exchange rate changes on cash and cash equivalents			0	0
Cash and Cash Equivalents, Period Increase (Decrease)			0	0
Cash and cash equivalents	$ 0	$ 0	$ 0	0	$ 0	$ 0
Proceeds from Issuance of Long-term Debt				0
Payments of Debt Issuance Costs				$ 0