Stockholders' Equity, Accumulated Other Comprehensive Income (Loss) and Noncontrolling Interest - Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Amortization of Defined Benefit Pension and Other Post-retirement Benefit Plan Items, Actuarial Loss [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Reclassifications out of AOCI	$ 2.4	$ 2.5
Amortization of Defined Benefit Pension and Other Post-retirement Benefit Plan Items, Prior Service Credits [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Reclassifications out of AOCI	(0.1)	(0.5)
Amortization of Defined Benefit Pension and Other Post-retirement Benefit Plan Items, Pension Settlement [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Reclassifications out of AOCI	0.2	0.4
Amortization of Defined Benefit Pension and Other Post-retirement Benefit Plan Items [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Reclassifications out of AOCI	2.5	2.4
Tax benefit	(0.5)	(0.6)
Net of tax	2.0	1.8
Accumulated Gain Loss Net Cash Flow Hedge Parent Realized Swap Interest Prior to De-Designation [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Realized swap interest		0.1
Accumulated Gain Loss Net Cash Flow Hedge Parent Realized Swap Interest Subsequent to De-Designation [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Realized swap interest	0.5
Cash Flow Hedge - Interest Rate Swap [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net of tax	(0.4)
Tax benefit	(0.1)
Net of tax	$ 0.4	$ 0.1