Stock-Based Compensation (Summary Of Restricted Stock Units) (Detail) (Restricted Stock Units [Member], USD $)	6 Months Ended
Jun. 30, 2012
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted- Average Grant-Date Fair Value, Unvested at December 31, 2011	$ 14.35
Weighted- Average Grant-Date Fair Value, Granted	$ 46.39
Weighted- Average Grant-Date Fair Value, Forfeited	$ 23.59
Weighted- Average Grant-Date Fair Value, Unvested at June 30, 2012	$ 22.07
Number of Shares, Unvested at December 31, 2011	101,617
Number of Shares, Granted	32,903
Number of Shares, Forfeited	(9,737)
Number of Shares, Unvested at June 30, 2012	124,783

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 number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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- Definition

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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