Summary of Significant Accounting Policies - Anti-dilutive Securities (Details) - shares shares in Thousands	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016
Stock options to purchase common stock
Anti-dilutive securities excluded from computations of diluted weighted-average common shares outstanding
Potentially dilutive securities excluded from computations of diluted weighted-average shares outstanding	8,601	7,306
Unvested RSUs
Anti-dilutive securities excluded from computations of diluted weighted-average common shares outstanding
Potentially dilutive securities excluded from computations of diluted weighted-average shares outstanding	47	89

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Name:	us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration