Summary and Changes in Stock Options Outstanding (Detail) - $ / shares shares in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Shares
Outstanding, Beginning Balance	6,356	6,112	5,507
Granted	1,040	1,807	1,077
Exercised	(1,592)	(1,353)	(341)
Canceled	(58)	(210)	(131)
Outstanding, Ending Balance	5,746	6,356	6,112
Weighted average exercise price
Outstanding, Beginning Balance	$ 28.83	$ 20.01	$ 15.63
Granted	84.97	46.55	40.19
Exercised	18.95	10.41	7.60
Canceled	64.67	43.05	34.35
Outstanding, Ending Balance	$ 41.38	$ 28.83	$ 20.01

The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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- Definition

Gross number of share options (or share units) granted during the period.

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

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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- Definition

Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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- Definition

Weighted average price at which option holders acquired shares when converting their stock options into shares.

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- Definition

Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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- Definition

Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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

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