Other Balance Sheet Items (Other Current Assets) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Prepaid registry fees, current	$ 24,513	$ 22,654
Prepaid expenses	31,189	17,920
Accounts Receivable, Net	5,062	4,642
Income Taxes Receivable, Current	4,091	3,572
Other Assets, Miscellaneous, Current	1,134	2,245
Other Assets, Current	$ 65,989	$ 51,033