Summary of Stock Option Activity (Detail) (Stock Options, USD $) In Millions, except Share data in Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding at December 31, 2011, Shares	2,707
Granted, Shares	685
Exercised, Shares	(60)
Forfeited and expired, Shares	(545)
Outstanding at Sept 30, 2012, Shares	2,787
Expected to vest at Sept 30, 2012, Shares	1,186
Exercisable at Sept 30, 2012, Shares	1,557
Outstanding at December 31, 2011, Weighted-Average Exercise Price	$ 56.81
Granted, Weighted-Average Exercise Price	$ 19.48
Exercised, Weighted-Average Exercise Price	$ 5.99
Forfeited and expired, Weighted-Average Exercise Price	$ 123.55
Outstanding at Sept 30, 2012, Weighted-Average Exercise Price	$ 35.49
Expected to vest at Sept 30, 2012,Weighted-Average Exercise Price	$ 27.64
Exercisable at Sept 30, 2012, Weighted-Average Exercise Price	$ 41.80
Outstanding at September 30, 2012, Weighted-Average Remaining Contractual Term(years)	2 years 7 months 10 days
Expected to vest at September 30, 2012, Weighted-Average Remaining Contractual Term(years)	3 years 9 months 7 days
Exercisable at September 30, 2012, Weighted-Average Remaining Contractual Term(years)	1 year 8 months 5 days
Outstanding at Sept 30, 2012, Aggregate Intrinsic Value	$ 9.0
Expected to vest at Sept 30, 2012, Aggregate Intrinsic Value	0.9
Exercisable at Sept 30, 2012, Aggregate Intrinsic Value	$ 8.1