Common Stock and Share-Based Compensation - Summary of Stock Option Activity (Detail) (USD $)	6 Months Ended
Jun. 30, 2014	Jun. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options outstanding at January 1, 2014	5,055,035
Granted	0	0
Forfeited and canceled	(401,734)
Exercised	(449,363)
Options outstanding at June 30, 2014	4,203,938
Options exercisable at June 30, 2014	4,072,329
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Options outstanding at January 1, 2014, Weighted average exercise price	$ 19.35
Granted, Weighted average exercise price	$ 0.00
Forfeited and canceled, Weighted average exercise price	$ 21.34
Exercised, Weighted average exercise price	$ 14.73
Options outstanding at June 30, 2014, Weighted average exercise price	$ 19.65
Options exercisable at June 30, 2014, Weighted average exercise price	$ 19.94
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Options outstanding at June 30, 2014, Weighted Average Contractual Life	3 years 5 months 23 days
Options exercisable at June 30, 2014, Weighted Average Contractual Life	3 years 4 months 6 days
Options outstanding at June 30, 2014, Aggregate Intrinsic Value	$ 5,809,572
Options exercisable at June 30, 2014, Aggregate Intrinsic Value	$ 4,915,061

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

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

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