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Number of common shares reserved for future issuance related to deferred compensation arrangements with individuals.

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Unrecognized cost of unvested share-based compensation awards.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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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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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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The number of shares purchased on the open market during the period for issuance to employees under the plan.

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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.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

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Purchase price of common stock expressed as a percentage of its fair value.

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Stock-Based Compensation - Additional Information (Detail) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	Feb. 28, 2018	Feb. 28, 2017 shares	Dec. 31, 2018 USD ($) Offering $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Jan. 31, 2018 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant \| shares			5,300,000
Stock-based compensation expense			$ 12,510	$ 12,727	$ 8,023
Unrecognized stock-based compensation expense			$ 13,600
Unrecognized stock-based compensation, expected to be recognized, weighted average period			2 years 3 months 18 days
Fair value of options vested			$ 3,700	4,200	3,400
Intrinsic value of options exercised			14,900	2,800	8,600
Intrinsic value of options outstanding			$ 26,700	$ 7,300	$ 25,600
Weighted average fair value per share of options granted \| $ / shares			$ 19.48	$ 18.85	$ 16.13
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional shares reserved for issuance under the plan \| shares			1,000,000
Stock-based compensation expense			$ 500	$ 700	$ 600
Number of offerings per year \| Offering			2
Amount withheld from employees			$ 1,700	$ 1,900	$ 1,700
Employee stock purchase plan, shares purchased \| shares			34,798	40,968	33,357
Maximum [Member] \| Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase price as a percentage of fair market value			85.00%
Chief Executive Officers [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense				$ 3,600
Equity Incentive Plan [Member] \| 2010 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional shares reserved for issuance under the plan \| shares		1,024,868				1,027,620
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 3,355	5,223	$ 3,777
Vesting period			4 years
Stock options exercisable \| shares			576,842
Weighted average exercise price \| $ / shares			$ 50.10
Weighted average remaining contractual life			4 years
Stock Options [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options contractual term range			7 years
Stock Options [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options contractual term range			10 years
Performance Share Unit [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years	3 years
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 5,930	6,526	3,386
Vesting period			4 years
Restricted Stock Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 487	$ 318	$ 308
Restricted stock awards units vest over, period			1 year
Performance Share Units and Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSU's vested and not issued during the period \| shares			54,688