Earnings Per Share Computation (Detail) (USD $) Share data in Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income	$ 689,800,000	$ 530,100,000	$ 328,000,000
Less: Income allocated to participating securities	12,500,000	10,000,000	6,100,000
Net income available to common shareholders	$ 677,300,000	$ 520,100,000	$ 321,900,000
Weighted average common shares outstanding	79.3	83.3	85.8
Dilutive common share equivalents from share-based compensation plans	1.4	1.1	1.5
Weighted average common and common equivalent shares outstanding, assuming dilution	80.7	84.4	87.3