Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Restricted Cash and Cash Equivalents Items [Line Items]
Current restricted cash	$ 34,387	$ 48,515
Non-current restricted cash	15,700	14,700
Held in Trust Deposits
Restricted Cash and Cash Equivalents Items [Line Items]
Current restricted cash	32,400	42,300
Held for Advertising Activity Deposits
Restricted Cash and Cash Equivalents Items [Line Items]
Current restricted cash	$ 1,900	$ 6,200

Amount of cash and cash equivalents restricted as to withdrawal or usage, classified as noncurrent. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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