Stock-Based Compensation - Additional Information (Details) $ in Millions	3 Months Ended
Mar. 31, 2019 USD ($) shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total unamortized compensation costs, net of estimated forfeitures related to unvested stock options	$ 13.2
Unamortized compensation costs related to unvested stock options, expected period of recognition	2 years 2 months 12 days
Restricted Stock Units ("RSUs")
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unamortized compensation costs related to unvested stock options, expected period of recognition	2 years 7 months 6 days
Total unamortized compensation costs, net of estimated forfeitures related to restricted stock unit	$ 39.5
Performance Based Restricted Stock Units ("PRSU")
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Performance period	2 years
Number of share unit granted \| shares	202,738
Performance Based Restricted Stock Units ("PRSU") \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Performance threshold	75.00%
Performance target to be earned at performance threshold	50.00%
Fair value of shares granted	$ 0.0
Performance Based Restricted Stock Units ("PRSU") \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Performance threshold	125.00%
Performance target to be earned at performance threshold	200.00%
Fair value of shares granted	$ 19.5
ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total unamortized compensation costs, net of estimated forfeitures related to unvested stock options	$ 0.9
Unamortized compensation costs related to unvested stock options, expected period of recognition	8 months 12 days

Percentage of performance target to be earned at performance threshold.

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- Definition

Share based compensation arrangement by share based payment award equity instruments other than options grants in period fair value.

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- Definition

Share based compensation arrangement by share based payment award performance period.

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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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

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Unrecognized cost of unvested options awarded to employees as compensation.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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