Condensed Consolidating Financials Condensed Consolidating Income Statement (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues									$ 599,030	$ 520,801	$ 371,396
Cost of revenues									105,989	86,893	67,013
Gross Profit	138,145	124,974	119,186	110,736	115,857	105,987	118,682	93,382	493,041	433,908	304,383
Selling and Marketing Expense									141,967	131,317	62,825
Research and Development Expense									30,680	25,485	18,624
General and Administrative Expense									134,188	101,683	60,772
Operating Expenses									306,835	258,485	142,221
Operating Income (Loss)									186,206	175,423	162,162
Income (Loss) from Subsidiaries, before Tax									0	0	0
Interest expense (income), net									31,204	21,254	7,650
Other expense (income), net									(165)	11,472	(410)
Income before income taxes									155,167	142,697	154,922
Income tax expense									29,840	35,175	33,259
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	32,754	28,759	35,049	28,765	20,754	27,806	36,040	22,922	125,327	107,522	121,663
Net Income (Loss) Attributable to Noncontrolling Interest									0	0	83
Preferred Stock Redemption Premium									991	0	0
Net earnings attributable to j2 Global, Inc. common shareholders	31,763	28,759	35,049	28,765	20,754	27,806	36,040	22,922	124,336	107,522	121,580
j2 Global, Inc. [Member]
Revenues									0	0	0
Cost of revenues									0	0	0
Gross Profit									0	0	0
Selling and Marketing Expense									0	0	0
Research and Development Expense									0	0	0
General and Administrative Expense									6,401	0	0
Operating Expenses									6,401	0	0
Operating Income (Loss)									(6,401)	0	0
Income (Loss) from Subsidiaries, before Tax									135,838	0	0
Interest expense (income), net									10,442	0	0
Other expense (income), net									(23)	0	0
Income before income taxes									119,018	0	0
Income tax expense									(6,309)	0	0
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest									125,327	0	0
Net Income (Loss) Attributable to Noncontrolling Interest									0	0	0
Preferred Stock Redemption Premium									991
Net earnings attributable to j2 Global, Inc. common shareholders									124,336	0	0
j2 Cloud Services, Inc. [Member]
Revenues									227,860	255,413	222,203
Cost of revenues									51,391	84,655	85,826
Gross Profit									176,469	170,758	136,377
Selling and Marketing Expense									36,414	41,555	35,677
Research and Development Expense									14,055	12,977	11,878
General and Administrative Expense									30,300	37,634	35,558
Operating Expenses									80,769	92,166	83,113
Operating Income (Loss)									95,700	78,592	53,264
Income (Loss) from Subsidiaries, before Tax									77,051	61,551	91,539
Interest expense (income), net									20,478	9,292	3,911
Other expense (income), net									141	(369)	(168)
Income before income taxes									152,132	131,220	141,060
Income tax expense									16,294	23,698	19,480
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest									135,838	107,522	121,580
Net Income (Loss) Attributable to Noncontrolling Interest									0	0	0
Preferred Stock Redemption Premium									0
Net earnings attributable to j2 Global, Inc. common shareholders									135,838	107,522	121,580
Non-Guarantor Subsidiaries [Member]
Revenues									412,217	369,079	206,045
Cost of revenues									95,386	105,480	38,039
Gross Profit									316,831	263,599	168,006
Selling and Marketing Expense									105,812	90,211	27,148
Research and Development Expense									16,625	12,508	6,746
General and Administrative Expense									97,487	64,049	25,214
Operating Expenses									219,924	166,768	59,108
Operating Income (Loss)									96,907	96,831	108,898
Income (Loss) from Subsidiaries, before Tax									0	0	0
Interest expense (income), net									284	11,962	3,739
Other expense (income), net									(283)	11,841	(242)
Income before income taxes									96,906	73,028	105,401
Income tax expense									19,855	11,477	13,779
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest									77,051	61,551	91,622
Net Income (Loss) Attributable to Noncontrolling Interest									0	0	83
Preferred Stock Redemption Premium									0
Net earnings attributable to j2 Global, Inc. common shareholders									77,051	61,551	91,539
Consolidation, Eliminations [Member]
Revenues									(41,047)	(103,691)	(56,852)
Cost of revenues									(40,788)	(103,242)	(56,852)
Gross Profit									(259)	(449)	0
Selling and Marketing Expense									(259)	(449)	0
Research and Development Expense									0	0	0
General and Administrative Expense									0	0	0
Operating Expenses									(259)	(449)	0
Operating Income (Loss)									0	0	0
Income (Loss) from Subsidiaries, before Tax									(212,889)	(61,551)	(91,539)
Interest expense (income), net									0	0	0
Other expense (income), net									0	0	0
Income before income taxes									(212,889)	(61,551)	(91,539)
Income tax expense									0	0	0
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest									(212,889)	(61,551)	(91,539)
Net Income (Loss) Attributable to Noncontrolling Interest									0	0	0
Preferred Stock Redemption Premium									0
Net earnings attributable to j2 Global, Inc. common shareholders									$ (212,889)	$ (61,551)	$ (91,539)