Other Balance Sheet Items (Other Current Assets) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Contingent consideration proceeds	$ 15,200
Prepaid registry fees, current	22,286	$ 21,717
Estimated contingent consideration receivable	0	14,721
Prepaid expenses	16,611	19,818
Accounts Receivable, Net	5,047	1,524
Other Assets, Miscellaneous, Current	2,919	2,750
Other Assets, Current	$ 46,863	$ 60,530