Accumulated Other Comprehensive Loss - Components of Accumulated Other Comprehensive Loss, Net of Tax (Details) $ in Thousands	9 Months Ended
Sep. 30, 2017 USD ($)
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance, December 31, 2016	$ 293,735
Ending balance, September 30, 2017	332,206
Foreign Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance, December 31, 2016	2,742
Net current period other comprehensive income	(1,344)
Reclassifications	0
Ending balance, September 30, 2017	1,398
Net Unrealized (Gains) Losses on Available-For-Sale Investments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance, December 31, 2016	37
Net current period other comprehensive income	(43)
Reclassifications	0
Ending balance, September 30, 2017	(6)
Accumulated Other Comprehensive Loss (Income) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance, December 31, 2016	2,779
Net current period other comprehensive income	(1,387)
Reclassifications	0
Ending balance, September 30, 2017	$ 1,392

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Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 55
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=84158357&loc=d3e1436-108581

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
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-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669686-108580

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Amount after tax of reclassification adjustments of other comprehensive income (loss) attributable to parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669686-108580

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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=84158357&loc=d3e1436-108581

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

+ References

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(30))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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