Long-Term Incentive Employee Compensation Rollforward of Outstanding Restricted Stock (Detail) - RSUs and PSUs [Member] - $ / shares shares in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Outstanding – January 1		0.8	1.0	1.2
Granted		0.3	0.3	0.3
Performance adjustment(a)	[1]	0.0	0.1	0.1
Vested and issued		(0.3)	(0.5)	(0.6)
Forfeited		(0.1)	(0.1)	0.0
Outstanding – December 31		0.7	0.8	1.0
Vested pending issuance		0.1	0.2	0.2
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Outstanding – January 1		$ 59.25	$ 51.24	$ 42.94
Granted		90.14	61.13	60.91
Performance adjustment(a)		0	57.88	44.87
Vested and issued		57.36	44.86	38.03
Forfeited		68.18	59.50	0
Outstanding – December 31		71.21	59.25	51.24
Vested pending issuance		$ 65.25	$ 57.88	$ 44.87

[1] Represents an adjustment for performance results achieved related to outstanding PSU shares that vested during the period and are pending issuance.