Stock-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Shares, Outstanding, Beginning Balance (in shares)	3,838,060
Shares, Granted (in shares)	1,219,725
Shares, Exercised (in shares)	(219,732)
Shares, Forfeited or expired (in shares)	(304,259)
Shares, Outstanding, Ending Balance (in shares)	4,533,794	3,838,060
Shares, Exercisable (in shares)	2,704,057
Shares, Vested and expected to vest (in shares)	4,352,976
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted- Average Exercise Price, Outstanding, Beginning Balance (in dollars per share)	$ 18.93
Weighted- Average Exercise Price, Granted (in dollars per share)	20.09
Weighted- Average Exercise Price, Exercised (in dollars per share)	2.02
Weighted- Average Exercise Price, Forfeited or expired (in dollars per share)	24.13
Weighted- Average Exercise Price, Outstanding, Ending Balance (in dollars per share)	19.71	$ 18.93
Weighted- Average Exercise Price, Exercisable (in dollars per share)	16.86
Weighted- Average Exercise Price, Vested and expected to vest (in dollars per share)	$ 19.48
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted- Average Remaining Contractual Term, Outstanding	7 years 2 months 19 days	7 years
Weighted- Average Remaining Contractual Term, Exercisable	6 years 2 months 12 days
Weighted- Average Remaining Contractual Term, Vested and expected to vest	7 years 2 months 12 days
Aggregate Intrinsic Value, Outstanding, Ending Balance	$ 18,050
Aggregate Intrinsic Value, Exercisable	17,254
Aggregate Intrinsic Value, Vested and expected to vest	$ 17,993
Weighted-average grant-date fair value of options granted (in dollars per share)	$ 12.56
Intrinsic value of options exercised	$ 3,700
Cash received for options exercised	400
Fair value of shares vested	10,700
Unrecognized compensation expense related to non-vested stock-options, net of related forfeiture estimates	$ 23,700
Unrecognized compensation expense recognition period	2 years 6 months

Unrecognized cost of unvested share-based compensation awards.

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.