Activity for Stock Option (Detail) (Stock Options, USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Stock Options
Number of Option Shares
Outstanding at beginning of period	2,263,000
Granted	760,000
Exercised	(215,000)
Cancelled/expired/forfeited	(80,000)
Outstanding at end of period	2,728,000	[1]
Exercisable at end of period	1,581,000
Weighted-Average Exercise Price
Outstanding at beginning of period	$ 10.96
Granted	$ 14.33
Exercised	$ 4.42
Cancelled/expired/forfeited	$ 16.90
Outstanding at end of period	$ 12.24	[1]
Exercisable at end of period	$ 9.19
Weighted-Average Remaining Contractual Term
Outstanding at end of period	4 years 2 months 12 days	[1]
Exercisable at end of period	1 year 10 months 24 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value, outstanding	$ 5.4	[1]
Aggregate Intrinsic Value, exercisable	$ 5.4

[1] Of the remaining shares subject to outstanding options, we expect approximately 1.1 million shares to vest at a weighted-average exercise price of $16.45.