Description Of Business And Summary Of Significant Accounting Policies (Narrative) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended
	Aug. 31, 2007 Rate	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Apr. 16, 2013 Rate	Aug. 15, 2007 Rate
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Convertible debenture, interest rate	3.25%				4.625%	3.25%
Convertible debenture, maturity date	Aug. 15, 2037
Net remeasurement gain (loss) on foreign currency translation		$ 1.0	$ (3.1)	$ (0.9)
Gains (losses) on foreign currency forward contracts		1.0	1.5
Advertising expenses		10.4	13.2	10.2
Derivative, Notional Amount		$ 29.7
Building Improvements [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment (years)		10 years
Maximum [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
RegistrationTerm		10 years
Average Service Term		2 years
Maximum [Member] | Buildings [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment (years)		47 years
Maximum [Member] | Computer Equipment, Purchased Software, Office Equipment, And Furniture And Fixtures [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment (years)		5 years
Minimum [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
RegistrationTerm		1 year
Average Service Term		1 year
Minimum [Member] | Buildings [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment (years)		35 years
Minimum [Member] | Computer Equipment, Purchased Software, Office Equipment, And Furniture And Fixtures [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment (years)		3 years