Unrestricted Subsidiaries Unrestricted Subsidiaries (Results of Operations) (Details) (USD $) In Thousands, 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
Revenues	$ 371,396								$ 371,396	$ 330,159	$ 255,394
Cost of Goods Sold, Subscription									67,013	60,613	44,086
Gross Profit	83,375	76,943	73,278	70,788	70,411	71,025	70,518	57,592	304,383	269,546	211,308
Selling and Marketing Expense									62,825	59,066	46,332
Research and Development Expense									18,624	16,373	12,827
General and Administrative Expense									60,772	58,157	48,226
Operating Expenses									142,221	133,596	107,385
Operating Income (Loss)									162,162	135,950	103,923
Other Nonoperating Income									1,805	1,313	6,818
Other Nonoperating Expense									(9,045)	(147)	(104)
Interest and other income (expense), net									(7,240)	1,166	6,714
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest									154,922	137,116	110,637
Income tax expense									33,259	22,350	27,590
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest									121,663	114,766	83,047
Net Income (Loss) Attributable to Noncontrolling Interest									83	0	0
Net earnings attributable to j2 Global, Inc. common shareholders	30,203								121,580	114,766	83,047
Ziff Davis, Inc [Member]
Revenues	9,712
Cost of Goods Sold, Subscription	1,956
Gross Profit	7,756
Selling and Marketing Expense	2,677
Research and Development Expense	151
General and Administrative Expense	2,039
Operating Expenses	4,867
Operating Income (Loss)	2,889
Other Nonoperating Income	0
Other Nonoperating Expense	0
Interest and other income (expense), net	0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	2,889
Income tax expense	1,192
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	1,697
Net Income (Loss) Attributable to Noncontrolling Interest	83
Net earnings attributable to j2 Global, Inc. common shareholders	$ 1,614