Revenue from Contracts with Customers - Disaggregation of Revenue (Details) $ in Thousands	3 Months Ended
Mar. 31, 2020 USD ($) division	Mar. 31, 2019 USD ($)
Disaggregation of Revenue [Line Items]
Revenue	$ 764,302	$ 706,508
Number of divisions \| division	2
Web Division
Disaggregation of Revenue [Line Items]
Revenue	$ 405,995	374,202
Media and Carrier Division
Disaggregation of Revenue [Line Items]
Revenue	358,307	332,306
U.S.
Disaggregation of Revenue [Line Items]
Revenue	428,930	418,200
International
Disaggregation of Revenue [Line Items]
Revenue	$ 335,372	$ 288,308

Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Name:	us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration