Share-Based Compensation Plans - Total Compensation Expense for Share-Based Payment Arrangements to Employees (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Share-Based Compensation Expense	$ 107.9	$ 130.9	$ 128.0
Tax Benefits Recognized	26.7	32.5	48.7
Restricted Stock Unit Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Share-Based Compensation Expense	81.4	96.3	87.3
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Share-Based Compensation Expense	1.4	2.6	9.0
Performance Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Share-Based Compensation Expense	$ 25.1	$ 32.0	$ 31.7