Earnings Per Share (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
Earnings Per Share Reconciliation [Abstract]
Net earnings attributable to j2 Global, Inc. common shareholders	$ 30,203								$ 121,580	$ 114,766	$ 83,047
Net earnings available to participating securities									(2,075)	(1,932)	0
Net earnings available to common shareholders									$ 119,505	$ 112,834	$ 83,047
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
Dilutive effect of equity incentive plans									321,946	585,233	1,363,807
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
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
Share options excluded from the computation of diluted earnings per share									527,319	421,319	551,130