Condensed Consolidating Financials Condensed Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Total revenues	$ 273,174	$ 211,800	$ 527,843	$ 412,302
Cost of revenues	43,159	35,591	83,969	69,878
Gross profit	230,015	176,209	443,874	342,424
Operating expenses:
Selling and Marketing Expense	80,862	48,617	158,339	96,729
Research and Development Expense	11,555	9,213	23,307	18,201
General and Administrative Expense	79,038	59,434	155,693	115,211
Total operating expenses	171,455	117,264	337,339	230,141
Income from operations	58,560	58,945	106,535	112,283
Income (Loss) from Subsidiaries, before Tax	0	0	0	0
Interest (income) expense, net	13,670	10,301	26,079	20,534
Other expense (income), net	4,227	(213)	4,551	(87)
Income before income taxes	40,663	48,857	75,905	91,836
Income tax expense	9,287	15,087	18,709	28,123
Net Income (Loss) Attributable to Parent	31,376	33,770	57,196	63,713
j2 Global, Inc. [Member]
Total revenues	0	0	0	0
Cost of revenues	0	0	0	0
Gross profit	0	0	0	0
Operating expenses:
Selling and Marketing Expense	0	0	0	0
Research and Development Expense	0	0	0	0
General and Administrative Expense	9,678	5,078	14,502	9,750
Total operating expenses	9,678	5,078	14,502	9,750
Income from operations	(9,678)	(5,078)	(14,502)	(9,750)
Income (Loss) from Subsidiaries, before Tax	33,960	38,019	60,390	72,342
Interest (income) expense, net	(5,284)	1,591	(10,593)	3,462
Other expense (income), net	0	(300)	0	(209)
Income before income taxes	29,566	31,650	56,481	59,339
Income tax expense	(1,809)	(2,120)	(714)	(4,374)
Net Income (Loss) Attributable to Parent	31,375	33,770	57,195	63,713
j2 Cloud Services, LLC [Member]
Total revenues	60,706	66,254	136,042	122,639
Cost of revenues	18,341	16,992	35,568	34,481
Gross profit	42,365	49,262	100,474	88,158
Operating expenses:
Selling and Marketing Expense	10,845	10,260	21,655	20,888
Research and Development Expense	2,845	2,930	5,795	6,219
General and Administrative Expense	7,200	4,431	11,971	9,902
Total operating expenses	20,890	17,621	39,421	37,009
Income from operations	21,475	31,641	61,053	51,149
Income (Loss) from Subsidiaries, before Tax	39,948	20,786	57,776	48,482
Interest (income) expense, net	5,545	5,193	10,752	10,425
Other expense (income), net	(129)	(93)	(175)	(1,013)
Income before income taxes	56,007	47,327	108,252	90,219
Income tax expense	14,750	9,308	21,239	17,877
Net Income (Loss) Attributable to Parent	41,257	38,019	87,013	72,342
Non-Guarantor Subsidiaries [Member]
Total revenues	224,039	166,079	431,927	321,645
Cost of revenues	36,389	39,087	88,520	67,288
Gross profit	187,650	126,992	343,407	254,357
Operating expenses:
Selling and Marketing Expense	70,017	38,402	136,691	75,932
Research and Development Expense	8,710	6,283	17,512	11,982
General and Administrative Expense	62,160	49,925	129,220	95,559
Total operating expenses	140,887	94,610	283,423	183,473
Income from operations	46,763	32,382	59,984	70,884
Income (Loss) from Subsidiaries, before Tax	0	0	0	0
Interest (income) expense, net	13,409	3,517	25,920	6,647
Other expense (income), net	4,356	180	4,726	1,135
Income before income taxes	28,998	28,685	29,338	63,102
Income tax expense	(3,654)	7,899	(1,816)	14,620
Net Income (Loss) Attributable to Parent	32,652	20,786	31,154	48,482
Consolidation, Eliminations [Member]
Total revenues	(11,571)	(20,533)	(40,126)	(31,982)
Cost of revenues	(11,571)	(20,488)	(40,119)	(31,891)
Gross profit	0	(45)	(7)	(91)
Operating expenses:
Selling and Marketing Expense	0	(45)	(7)	(91)
Research and Development Expense	0	0	0	0
General and Administrative Expense	0	0	0	0
Total operating expenses	0	(45)	(7)	(91)
Income from operations	0	0	0	0
Income (Loss) from Subsidiaries, before Tax	(73,908)	(58,805)	(118,166)	(120,824)
Interest (income) expense, net	0	0	0	0
Other expense (income), net	0	0	0	0
Income before income taxes	(73,908)	(58,805)	(118,166)	(120,824)
Income tax expense	0	0	0	0
Net Income (Loss) Attributable to Parent	$ (73,908)	$ (58,805)	$ (118,166)	$ (120,824)