Summary of Stock Option Activity (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Total Intrinsic Value	$ 0.5	$ 1.7	$ 6.1
Shares Subject To Options
Beginning Balance	1,105,600	1,265,600	1,610,368
Options exercised	(20,000)	(160,000)	(344,768)
Options canceled			(344,768)
Ending Balance	1,085,600	1,105,600	1,265,600	1,610,368
Exercisable at end of year	1,085,600
Weighted Average Exercise Price Per Share
Beginning Balance	$ 21.78	$ 22.07	$ 20.16
Options exercised	$ 12.34	$ 24.10
Options canceled			$ 13.14
Ending Balance	$ 21.95	$ 21.78	$ 22.07	$ 20.16
Exercisable at end of year	$ 21.95
Weighted Average Outstanding Contractual Life (in years)
Weighted Average Outstanding Contractual Life (in years)	3 years 1 month 1 day	4 years 6 days	4 years 10 months 21 days	4 years 10 months 21 days
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition	1 year 4 months 25 days