Description Of Business And Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
adjustments to current assets	$ 19,700
adjustments to non current assets	7,600
adjustments to accumulated deficit	22,500
Capitalized Computer Software, Additions	14,700	$ 17,700
Net remeasurement gain (loss) on foreign currency translation	1,000	1,000
Gains (losses) on foreign currency forward contracts	1,000	1,000
Advertising expenses	15,200	27,400	$ 17,200
Derivative, Notional Amount	28,500
Deferred Tax Liabilities, Net, Noncurrent	134	444,108
Deferred Tax Liabilities, Other	5,352	3,116
adjustments to deferred tax liability	$ 4,800
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]
Registration Payment Arrangement, Term	one
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
Additional Paid-in Capital [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption			2,544
Retained Earnings [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption		$ 22,512	$ 32,916