Share-Based Compensation Plans - Outstanding Restricted Stock Unit Awards (Detail) - Restricted Stock Unit Awards - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
NUMBER
Balance at beginning of period (in shares)	3,121,842
Granted (in shares)	855,112
Distributed (in shares)	(1,271,190)
Forfeited (in shares)	(61,002)
Balance at end of period (in shares)	2,644,762
Units Convertible, at the end of year (in shares)	23,435
AGGREGATE INTRINSIC VALUE
AGGREGATE INTRINSIC VALUE	$ 281.0	$ 261.0
Units Convertible, at the end of year	$ 2.5