Stockholders' Equity - Activities Under Equity Plan (Details)	3 Months Ended
Mar. 31, 2019 shares
ESPP
Share-based Compensation Arrangement By Share-based Payment Award, Shares Authorized [Roll Forward]
Shares available for grant (shares)	208,159
ESPP common stock purchased by eligible employees (shares)	0
Shares available for grant (shares)	208,159
Restricted stock units \| 2012 Equity Plan
Share-based Compensation Arrangement By Share-based Payment Award, Shares Authorized [Roll Forward]
Shares available for grant (shares)	904,437
Shares available for grant (shares)	663,849
Eligible Employees \| Restricted stock units \| 2012 Equity Plan
Share-based Compensation Arrangement By Share-based Payment Award, Shares Authorized [Roll Forward]
RSU and restricted stock awarded to eligible employees, net of forfeitures (shares)	(240,588)

Share-based Compensation Arrangement By Share-based Payment Award, Shares Authorized [Roll Forward]

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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

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- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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- Definition

Number of share options (or share units) exercised during the current period.

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