Basis Of Presentation (Details) (USD $)	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
Identifiable intangible assets minimum useful life (years)									1 year 6 months
Advertising Expense									$ 48,100,000	$ 45,400,000	$ 36,300,000
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	1,400,000				(800,000)				1,400,000	(800,000)	(700,000)
Revenues	371,396,000								371,396,000	330,159,000	255,394,000
Net earnings	30,203,000								121,580,000	114,766,000	83,047,000
Basic earnings per share	$ 0.66	$ 0.69	$ 0.68	$ 0.61	$ 0.63	$ 0.55	$ 0.63	$ 0.69	$ 2.63	$ 2.46	$ 1.86
Diluted earnings per share	$ 0.65	$ 0.69	$ 0.67	$ 0.60	$ 0.62	$ 0.54	$ 0.61	$ 0.66	$ 2.61	$ 2.43	$ 1.81
Foreign Currency Transaction Gain (Loss), Realized									(100,000)	0	200,000
Remaining Service Obligations To eFax Customers [Member]
Revenues										10,300,000
Net earnings										$ 7,600,000
Basic earnings per share										$ 0.17
Diluted earnings per share										$ 0.16
Minimum [Member]
Identifiable intangible assets minimum useful life (years)									1 year
Property, Plant and Equipment, Useful Life									1 year
Maximum [Member]
Identifiable intangible assets minimum useful life (years)									20 years
Property, Plant and Equipment, Useful Life									7 years