Share-Based Compensation Plans - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonqualified stock option grants	446,868
Stock options granted, total grant-date fair value	$ 5.5
Share-Based Compensation Expense	20.5	24.2
Stock Unit
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock unit awards granted	1,149,213
Stock unit awards, total grant-date fair value	60.6
Performance Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock unit awards granted	296,650
Stock unit awards, total grant-date fair value	15.6
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-Based Compensation Expense	6.9	11.2
Stock Options | Retirement Eligible Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-Based Compensation Expense	2.1	5.3
Stock and Stock Unit Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-Based Compensation Expense	12.4	12.7
Stock and Stock Unit Awards | Fully Vested RSU Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-Based Compensation Expense	$ 1.5	$ 2.3