Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

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).

+ 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 (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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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

Number of additional shares authorized for issuance under share-based payment arrangement.

+ References

No definition available.

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- Definition

Number of shares authorized for issuance 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)(3)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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- Definition

Gross number of share options (or share units) granted during the period.

+ References

No definition available.

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- Definition

Number of shares issued 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
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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- Definition

Represents the number of annual installment vesting periods.

+ References

No definition available.

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- Definition

Represents the annual increase in maximum number of shares (or other type of equity) approved (usually by shareholders and board of directors), for awards under the equity-based compensation plan.

+ References

No definition available.

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- Definition

Represents the annual percentage increase in maximum number of shares (or other type of equity) approved (usually by shareholders and board of directors), for awards under the equity-based compensation plan.

+ References

No definition available.

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Stock Based Compensation (Details)		3 Months Ended
Stock Based Compensation (Details)	Dec. 02, 2013 shares	Mar. 31, 2020 item shares	Mar. 31, 2019 shares	Dec. 31, 2019 shares
Stock-based compensation
Common stock, shares issued		57,001,253		56,902,301
Employee stock options
Stock-based compensation
Options granted (in shares)		1,137,420	1,342,447
ESPP
Stock-based compensation
Total number of shares of common stock available for issuance		581,286
Awards issued under the plan (in shares)		417,277
Increase in shares of common stock available for issuance (in shares)		0
ESPP \| Maximum
Stock-based compensation
Annual percentage increase in shares of common stock available for issuance		1.00%
Annual increase in shares of common stock available for issuance (in shares)		621,814
Restricted stock units
Stock-based compensation
Awards issued under the plan (in shares)		327,103
Granted		221,604
Annual installment vesting periods \| item		3
The 2013 Plan
Stock-based compensation
Total number of shares of common stock available for issuance		12,300,969
Annual percentage increase in shares of common stock available for issuance		4.00%
Awards issued under the plan (in shares)		10,030,935
Increase in shares of common stock available for issuance (in shares)		1,138,046
The 2010 Plan
Stock-based compensation
Total number of shares of common stock available for issuance		2,684,456
Options granted (in shares)	0