Employee Stock Benefit Plans - Restricted Stock and Restricted Stock Units Activity (Details) - $ / shares	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Weighted-Average Grant Date Fair Value (in dollars per share)
Granted (in dollars per share)	$ 12.97	$ 18.69	$ 22.74
Restricted stock units
RSUs
Outstanding beginning balance (in shares)	227,088
Granted (in shares)	613,650
Vested (in shares)	(92,031)
Forfeited (in shares)	(134,434)
Outstanding ending balance (in shares)	614,273	227,088
Weighted-Average Grant Date Fair Value (in dollars per share)
Outstanding beginning balance (in dollars per share)	$ 37.69
Granted (in dollars per share)	20.04
Vested (in dollars per share)	35.79
Forfeited (in dollars per share)	26.17
Outstanding ending balance (in dollars per share)	$ 22.83	$ 37.69

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(3)
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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

+ References

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-Publisher FASB
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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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-Paragraph 2
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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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No definition available.

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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-Publisher FASB
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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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- Definition

Net number of non-option equity instruments granted to participants.

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-Name Accounting Standards Codification
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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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