Revenues - Additional Information (Details) - ASC 606 [Member] $ in Thousands	3 Months Ended
Mar. 31, 2019 USD ($)
Direct Advertising Expenses (Exclusive of Depreciation and Amortization) [Member]
Capitalized Contract Cost [Line Items]
Contract cost expense net	$ 1,119
Other Current Assets [Member]
Capitalized Contract Cost [Line Items]
Capitalized contract cost, net	$ 5,814

Amount, after accumulated amortization and accumulated impairment loss, of asset recognized from cost incurred to obtain or fulfill contract with customer.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 340
-SubTopic 40
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=68051541&loc=SL49131252-203054

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