Amount of cash and cash equivalents restricted as to withdrawal or usage. 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_RestrictedCashAndCashEquivalents
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Restricted Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 29,563	$ 33,551	$ 44,349
Total cash, cash equivalents, and restricted cash shown in statements of cash flows	29,866	$ 33,854	44,712	$ 52,419
Prepaid expenses and other current assets
Restricted Cash and Cash Equivalents [Abstract]
Restricted cash	303		60
Other long-term assets
Restricted Cash and Cash Equivalents [Abstract]
Restricted cash	$ 0		$ 303