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Stock Incentive Plans and Stock Purchase Plan - Schedule of Weighted Average Grant Date Fair Values (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Shares, Non-vested shares at January 1, 2012	978,353
Number of Shares, Awarded	465,317
Number of Shares, Forfeited	(39,441)
Number of Shares, Vested	(423,331)
Number of Shares, Non-vested shares at December 31, 2012	980,898	978,353
Weighted Average Fair Value, Non-vested shares at January 1, 2012	$ 59.64
Weighted Average Fair Value, Awarded	$ 60.11	$ 70.99	$ 54.90
Weighted Average Fair Value, Forfeited	$ 65.06
Weighted Average Fair Value, Vested	$ 54.30
Weighted Average Fair Value, Non-vested shares at December 31, 2012	$ 61.94	$ 59.64

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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