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Share based compensation arrangement by share based payment award options vested and exercisable weighted average exercise price.

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Treasury Stock, Percentage of Outstanding Shares Reacquired

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Face amount or stated value per share of common stock.

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Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer.

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The maximum number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) permitted to be issued by an entity's charter and bylaws.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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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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- Definition

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

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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 grant-date intrinsic 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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Amount by which current fair value of underlying stock exceeds exercise price of fully vested and expected to vest exercisable or convertible options. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Price of a single share of a number of saleable stocks of a company.

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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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Amount of stock repurchase plan authorized.

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Amount remaining of a stock repurchase plan authorized.

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Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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Equity impact of the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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Total cost of shares repurchased divided by the total number of shares repurchased.

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Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.

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Shareholders' Equity and Share-Based Compensation - Narrative (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 $ / shares shares	Dec. 31, 2017 USD ($) $ / shares	Dec. 31, 2015 shares	Dec. 31, 2012	Sep. 30, 2015 USD ($) $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, par value (in usd per share)	$ 0.001	$ 0.001	$ 0.001
Shares reacquired during period (in shares) \| shares	899,468	52,095	129,112
Percentage of outstanding shares reacquired		0.10%	0.30%
Shares reacquired during period, value \| $		$ 2,200,000		$ 5,100,000
Share price of treasury stock acquired during period (in usd per share)	$ 32.68	$ 41.17		$ 39.41
Remaining authorized repurchase amount \| $	$ 20,600,000
Treasury stock (in shares) \| shares	24,902,579	24,850,484
Preferred stock, shares authorized (in shares) \| shares	1,000,000	1,000,000
Preferred stock, par value (in usd per share)	$ 0.001	$ 0.001
Fungible share pool, grant of full value share conversion ratio						2.5
Intrinsic value	0
Weighted average exercise prices of vested and exercisable options (in usd per share)	36.59	$ 34.81	$ 31.42
Share price (in usd per share)	$ 42.04
Aggregate intrinsic value of vested options \| $	$ 2,500,000
Aggregate intrinsic value of options \| $	$ 2,900,000
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period	7 years
Minimum \| Employee stock option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Minimum \| Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	1 year
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period	10 years
Maximum \| Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	5 years
2015 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized repurchase amount \| $							$ 50,000,000.0
Common stock, par value (in usd per share)							$ 0.001
Comprehensive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amended increase in shares reserved for issuance (in shares) \| shares					3,250,000
Shares available for grant (in shares) \| shares	751,661