Quarterly report pursuant to Section 13 or 15(d)

Cash, Cash Equivalents and Investments - Narrative (Details)

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Cash, Cash Equivalents and Investments - Narrative (Details)
3 Months Ended 9 Months Ended
Sep. 30, 2017
USD ($)
security
Sep. 30, 2017
USD ($)
security
Cash and Cash Equivalents [Abstract]    
Number of owned securities that were in an unrealized loss position | security 3 3
Other-than-temporary investment losses   $ 0
Unrealized losses deemed to be other-than-temporary, recognized $ 0 $ 0