Commitments And Contingencies (Narrative) (Details) number in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Commitments And Contingencies [Line Items]
Number of domain names registered	145.4
Uncertain tax positions	$ 229,200,000
ICANN Agreement [Member]
Commitments And Contingencies [Line Items]
Expiration Date of Registry Agreement	Nov. 30, 2024
Registry fee per transaction	$ 0.25
Payments for registry fees	34,700,000	$ 33,000,000.0	$ 32,300,000
.TV Agreement [Member]
Commitments And Contingencies [Line Items]
renewed agreement fees	$ 5,000,000.0	$ 5,000,000	$ 5,000,000