Consolidated Statements of Stockholders' Equity (Parenthetical) - Additional Paid-In Capital [Member] $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($)
Stated interest rate on convertible senior notes	4.25%
Offering costs for convertible senior notes	$ 543

Contractual interest rate for funds borrowed, under the debt agreement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant