Share-Based Compensation - Summary of Activity Related to Stock Options Granted under Company's Incentive Plan (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Shares outstanding, beginning balance	4,229
Total Shares, Granted	25
Total Shares, Exercised	(459)
Total Shares, Forfeited, canceled or expired	(19)
Total Shares outstanding, ending balance	3,776
Total Shares, Exercisable	2,247
Weighted Average Exercise Price per Share Outstanding, beginning balance	$ 14.57
Weighted Average Exercise Price per Share, Granted	$ 24.97
Weighted Average Exercise Price per Share, Exercised	$ 12.75
Weighted Average Exercise Price per Share, Forfeited, canceled or expired	$ 16.21
Weighted Average Exercise Price per Share Outstanding, ending balance	$ 14.85
Weighted Average Exercise Price per Share, Exercisable	$ 14.23
Weighted Average Remaining Contractual Term (Years), Outstanding	6 years 6 months 15 days
Weighted Average Remaining Contractual Term (Years), Exercisable	6 years 2 months 19 days
Aggregate Intrinsic Value, Outstanding	$ 39,804
Aggregate Intrinsic Value, Exercisable	$ 25,077
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Shares, Available for issuance	2,233

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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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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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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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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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For presentations that combine terminations, 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 or that expired.

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Weighted average price of options that were either forfeited or expired.

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

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of options outstanding.

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The number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance sheet date, including 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 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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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 can acquire the shares reserved for issuance on stock options awarded.

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

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