Stock-Based Compensation (Schedule Of Black-Scholes Assumptions Used For Stock Options) (Detail) (Stock Options [Member], USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Risk-free interest rate, minimum	0.68%	1.17%	0.68%	1.17%
Risk-free interest rate, maximum		1.78%	1.01%	2.34%
Estimated volatility, minimum	66.00%	86.00%	66.00%	81.00%
Estimated volatility, maximum			73.00%	86.00%
Estimated dividend yield
Weighted-average grant date fair value per share of options granted	$ 26.73	$ 7.00	$ 22.37	$ 13.54
Minimum [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Estimated term (in years)	5 years 3 months 11 days	5 years 10 months 17 days	5 years 3 months 11 days	5 years 10 months 17 days
Maximum [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Estimated term (in years)			5 years 5 months 23 days	5 years 11 months 27 days