Stock-based Compensation and Outstanding Awards - Summary of Stock Option Activity (Detail)	12 Months Ended
Dec. 31, 2017 $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Options, Outstanding, Beginning balance \| shares	4,853,000
Stock Options, Granted \| shares	915,000
Stock Options, Forfeited \| shares	(102,000)
Stock Options, Exercised \| shares	(36,000)
Stock Options, Outstanding, Ending balance \| shares	5,630,000
Stock Options, Exercisable at December 31, 2017 \| shares	3,964,000
Weighted average exercise price, Outstanding, Beginning balance \| $ / shares	$ 26.83
Weighted average exercise price, Granted \| $ / shares	20.64
Weighted average exercise price, Forfeited \| $ / shares	23.23
Weighted average exercise price, Exercised \| $ / shares	14.19
Weighted average exercise price, Outstanding, Ending balance \| $ / shares	25.97
Weighted average exercise price, Exercisable at December 31, 2017 \| $ / shares	$ 29.16
Weighted average remaining contractual term, Outstanding, Ending balance	4 years 10 months 24 days
Weighted average remaining contractual term, Exercisable at December 31, 2017	4 years 6 months

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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.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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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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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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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.

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

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

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

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

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, 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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Number of share options (or share units) exercised during the current period.

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