Summary of Significant Accounting Policies - Net Income per Share Schedule of Weighted Average Number of Shares (Details) - shares shares in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average common shares outstanding (in shares)	34,301	34,050	34,246	33,995
Less: Weighted average unvested restricted shares subject to repurchase (in shares)	5	3	5	4
Weighted average common shares outstanding; basic (in shares)	34,296	34,047	34,241	33,991
Plus: Weighted average options, restricted stock units and restricted shares used to compute diluted net income per common share (in shares)	1,369	1,374	1,421	1,415
Weighted average common shares outstanding; diluted (in shares)	35,665	35,421	35,662	35,406
PSUs and PSOs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares excluded from net loss per share computation (in shares)	130	361	130	361

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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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.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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This element represents the weighted average total number of shares issued throughout the period including the first (beginning balance outstanding) and last (ending balance outstanding) day of the period before considering any reductions (for instance, shares held in treasury) to arrive at the weighted average number of shares outstanding. Weighted average relates to the portion of time within a reporting period that common shares have been issued and outstanding to the total time in that period. Such concept is used in determining the weighted average number of shares outstanding for purposes of calculating earnings per share (basic).

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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Number of shares of restricted stock determined by relating the portion of time within a reporting period that restricted shares have been outstanding to the total time in that period. Restricted shares are subject to sales, contractual, regulatory or other restrictions that prevent or inhibit the holder from freely disposing of them before the restriction ends.

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