Stock option activity (Detail) (Stock Options, USD $) In Millions, except Share data in Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Outstanding at Beginning of Period	1,691
Shares Granted	103
Shares Exercised	(399)
Shares Outstanding at End of Period	1,395
Shares Exercisable	1,041
Weighted Average Exercise Price of Shares Outstanding at Beginning of Period	$ 20.98
Weighted Average Exercise Price of Shares Granted	$ 24.25
Weighted Average Exercise Price of Shares Exercised	$ 21.15
Weighted Average Exercise Price of Shares Outstanding at End of Period	$ 21.17
Weighted Average Exercise Price of Exercisable Shares	$ 20.15
Weighted Average Remaining Contractual Term of Outstanding Options	4 years 59 days
Weighted Average Remaining Contractual Term of Exercisable Option	3 years 166 days
Options Outstanding, Intrinsic Value	$ 19.4
Options, Exercisable, Intrinsic Value	$ 15.5