Earnings Per Share (Details) (USD $) In Thousands, except Share data, 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
Earnings Per Share Reconciliation [Abstract]
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
Undistributed Earnings (Loss) Allocated to Participating Securities, Basic									2,590	2,105	2,075
Net earnings available to common shareholders									$ 121,746	$ 105,417	$ 119,505
Basic	47,146,503	46,845,477	46,745,596	46,365,158	45,867,769	45,729,171	45,428,230	45,160,140	46,778,015	45,548,767	45,459,712
Dilutive effect of equity incentive plans									328,523	591,252	321,946
Diluted	47,468,841	47,163,912	47,067,767	46,765,732	46,382,363	46,291,631	46,018,245	45,668,167	47,106,538	46,140,019	45,781,658
Basic	$ 0.66	$ 0.60	$ 0.73	$ 0.61	$ 0.45	$ 0.60	$ 0.78	$ 0.50	$ 2.60	$ 2.31	$ 2.63
Diluted	$ 0.66	$ 0.60	$ 0.73	$ 0.60	$ 0.44	$ 0.59	$ 0.77	$ 0.49	$ 2.58	$ 2.28	$ 2.61
Share options excluded from the computation of diluted earnings per share									0	0	527,319