Stock-Based Compensation - Plan Information (Details)	9 Months Ended
Sep. 30, 2019 item
Stock-based compensation
Number of stock plans	4
Expiration period	10 years
Vesting percentage on first anniversary of grant date	25.00%
Remaining vesting period	3 years
Employee Stock Purchase Plan 2015
Stock-based compensation
Maximum employee contributions as a percentage of earnings under the ESPP	15.00%
Purchase price per share expressed as a percentage of the lower of the stock's fair market value on the offering date or purchase date under the ESPP	85.00%
First anniversary \| RSU
Stock-based compensation
Vesting (as a percent)	25.00%
Second anniversary \| RSU
Stock-based compensation
Vesting (as a percent)	25.00%
Third anniversary \| RSU
Stock-based compensation
Vesting (as a percent)	25.00%
Fourth anniversary \| RSU
Stock-based compensation
Vesting (as a percent)	25.00%

Maximum employee contributions as a percentage of earnings under the Employee Stock Purchase Plan (the ESPP).

No definition available.

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- Definition

Purchase price per share expressed as a percentage of the lower of the stock's fair market value on the offering date or purchase date under the Employee Stock Purchase Plan (the ESPP).

+ References

No definition available.

+ Details

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- Definition

Represents the remaining vesting period under the stock-based compensation plan, in 'PnYnMnDTnHnMnS' format.

+ References

No definition available.

+ Details

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- Definition

Represents the percentage of stock awards vesting on the first anniversary of the date of the grant.

+ References

No definition available.

+ Details

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- Definition

Represents the number of stock-based compensation plans.

+ References

No definition available.

+ Details

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- Definition

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.

+ References

No definition available.

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- Definition

Percentage of vesting of award under share-based payment arrangement.

+ References

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 (a)(1)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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- Definition

Period from grant date that an equity-based award expires, 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
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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