Summary of Stock Option Activity (Detail) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Shares Under Option
Outstanding at beginning of period	4,726
Exercised	(193)
Cancelled/forfeited/expired	(373)
Outstanding at end of period	4,160	4,726
Vested and expected to vest at end of period	4,119
Exercisable at end of period	1,249
Weighted Average Exercise Price
Outstanding at beginning of period	$ 18.90
Exercised	$ 10.42
Cancelled/forfeited/expired	$ 18.08
Outstanding at end of period	$ 19.36	$ 18.90
Vested and expected to vest at end of period	$ 19.42
Exercisable at end of period	$ 8.29
Weighted Average Remaining Contractual Term (years)
Outstanding	5 years 10 months 24 days	6 years 2 months 12 days
Vested and expected to vest at end of period	5 years 10 months 24 days
Exercisable at end of period	6 years
Aggregate Intrinsic Value
Outstanding at beginning of period	$ 2.1
Outstanding at end of period	11.5	2.1
Vested and expected to vest at end of period	11.4
Exercisable at end of period	$ 9.4