Other Balance Sheet Items Other Balance Sheet Items (Other long-term assets) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Balance Sheet Related Disclosures [Abstract]
Prepaid registry fees, noncurent	$ 7,730	$ 0
Restricted Cash and Investments, Noncurrent	9,295	9,288
Nontrade Receivables, Noncurrent	5,673	5,673
Other Assets, Miscellaneous, Noncurrent	3,609	3,642
Other Assets, Noncurrent	$ 26,307	$ 18,603

The noncurrent cash, cash equivalents and investments that is restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits classified as long-term; that is not expected to be released from such existing restrictions within one year of the balance sheet date or operating cycle, whichever is longer. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. Includes noncurrent cash equivalents and investments that are similarly restricted as to withdrawal, usage or disposal.

No definition available.

Name:	us-gaap_RestrictedCashAndInvestmentsNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant