Stock-Based Compensation - Summary of Stock Options Outstanding (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2013	Dec. 31, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Options, outstanding, Beginning Balance	6,035
Number of Options, granted
Number of Options, cancelled/forfeited	(46)
Number of Options, exercised	(4)
Number of Options, outstanding, Ending Balance	5,985	6,035
Number of Options, Options exercisable	3,528
Weighted Average Exercise Price, outstanding, Beginning Balance	$ 24.81
Weighted Average Exercise Price, granted
Weighted Average Exercise Price, cancelled/forfeited	$ 26.33
Weighted Average Exercise Price, exercised	$ 15.29
Weighted Average Exercise Price, outstanding, Ending Balance	$ 24.80	$ 24.81
Weighted Average Exercise Price, Options exercisable	$ 24.81
Weighted Average Remaining Contractual Life In Years, Options outstanding	6 years 5 months 16 days	6 years 8 months 9 days
Weighted Average Remaining Contractual Life In Years, Options exercisable	4 years 11 months 12 days
Aggregate Intrinsic Value, Options outstanding, Beginning Balance	$ 5,154
Aggregate Intrinsic Value, Options outstanding, Ending Balance	5,290	5,154
Aggregate Intrinsic Value, Options exercisable	$ 2,628

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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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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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