Quarterly Results (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Quarterly Results [Abstract]
Revenue, Net	$ 102,033	$ 93,246	$ 89,465	$ 86,652	$ 85,072	$ 86,027	$ 85,676	$ 73,384
Gross Profit	83,375	76,943	73,278	70,788	70,411	71,025	70,518	57,592	304,383	269,546	211,308
Net earnings attributable to j2 Global, Inc. common shareholders	$ 30,203								$ 121,580	$ 114,766	$ 83,047
Basic	$ 0.66	$ 0.69	$ 0.68	$ 0.61	$ 0.63	$ 0.55	$ 0.63	$ 0.69	$ 2.63	$ 2.46	$ 1.86
Diluted	$ 0.65	$ 0.69	$ 0.67	$ 0.60	$ 0.62	$ 0.54	$ 0.61	$ 0.66	$ 2.61	$ 2.43	$ 1.81
Basic	45,071,204	45,002,565	45,373,930	46,400,441	46,692,364	45,993,328	45,399,940	45,093,127	45,459,712	45,799,615	44,578,036
Diluted	45,423,502	45,340,111	45,569,564	46,794,603	46,989,376	46,455,584	46,723,792	46,558,543	45,781,658	46,384,848	45,941,843