Share-Based Compensation (Summary of Stock Option Activity) (Detail) (USD $) In Millions, except Share data, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Shares Under Option
Outstanding at December 31, 2011	3,995,000
Granted	1,221,000	200,000
Exercised	(197,000)
Cancelled/forfeited/expired	(276,000)
Outstanding at September 30, 2012	4,743,000		3,995,000
Exercisable at September 30, 2012	713,000
Weighted Average Exercise Price
Outstanding at December 31, 2011	$ 20.75
Granted	$ 13.22
Exercised	$ 7.09
Cancelled/forfeited/expired	$ 29.12
Outstanding at September 30, 2012	$ 18.89		$ 20.75
Exercisable at September 30, 2012	$ 7.09
Weighted Average Remaining Contractual Term (years)
Outstanding at December 31, 2011	6 years 6 months		5 years 10 months 24 days
Granted	9 years 4 months 24 days
Exercisable at September 30, 2012	6 years 4 months 24 days
Aggregate Intrinsic Value
Outstanding at December 31, 2011	$ 9.5
Outstanding at September 30, 2012	3.8		9.5
Exercisable at September 30, 2012	$ 2.5