Quarterly Results (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Results [Abstract]
Revenues	$ 251,837	$ 210,116	$ 211,800	$ 200,502	$ 204,823	$ 178,701	$ 176,038	$ 161,253
Gross profit	211,608	173,124	176,209	166,214	170,214	148,032	146,544	133,067	$ 727,155	$ 597,857	$ 493,041
Net Income	43,157	45,569	33,770	29,943	35,467	37,375	38,916	21,878	152,439	133,636	125,327
Net income attributable to j2 Global, Inc. common shareholders	$ 43,157	$ 45,569	$ 33,770	$ 29,943	$ 35,467	$ 37,375	$ 38,916	$ 21,878	$ 152,439	$ 133,636	$ 124,336
Net income per common share:
Basic (in dollars per share)	$ 0.90	$ 0.95	$ 0.69	$ 0.62	$ 0.73	$ 0.77	$ 0.81	$ 0.45	$ 3.15	$ 2.76	$ 2.60
Diluted (in dollars per share)	$ 0.89	$ 0.94	$ 0.69	$ 0.61	$ 0.72	$ 0.77	$ 0.80	$ 0.45	$ 3.13	$ 2.73	$ 2.58
Weighted average shares outstanding
Basic (in shares)	47,348,372	47,310,011	48,055,783	47,966,718	47,849,748	47,696,224	47,537,597	47,422,396	47,668,357	47,627,853	46,778,015
Diluted (in shares)	47,862,218	47,494,744	48,265,298	48,238,098	48,772,061	47,953,871	47,853,574	47,766,088	47,963,226	48,087,760	47,106,538