Aggregate number of common shares reserved for future issuance.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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

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 options outstanding, including both vested and non-vested options.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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Stockholders' Equity - Incentive Plans (Details) - shares	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stock options
Stock option and incentive plans
Outstanding (in shares)		3,754,320	2,239,044	1,799,226	1,670,574
2005 Plan
Stock option and incentive plans
Common stock reserved for issuance (in shares)		0
2005 Plan \| Stock options
Stock option and incentive plans
Outstanding (in shares)		364,420
2014 Plan
Stock option and incentive plans
Common stock reserved for issuance (in shares)	2,187,100	187,100
2014 Plan \| Stock options
Stock option and incentive plans
Outstanding (in shares)		3,389,900
2014 Plan \| Restricted stock
Stock option and incentive plans
Outstanding (in shares)		239,800