Restructuring, Impairment and Other - Schedule of Net Restructuring, Impairment and Other Expenses (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Restructuring Cost And Reserve [Line Items]
Employee Terminations	$ 2.5	$ 9.0	$ 6.3	$ 29.9
Other Restructuring Charges	4.5	6.7	16.1	24.8
Multi-Employer Pension Plan Charges	0.8	37.3	0.9	39.2
Impairment and Other	(3.8)	1.2	(3.8)	(0.1)
Total	4.0	54.2	19.5	93.8
Total Operating Segments | Business Services
Restructuring Cost And Reserve [Line Items]
Employee Terminations	2.2	4.6	3.6	16.7
Other Restructuring Charges	1.2	2.2	5.8	5.0
Multi-Employer Pension Plan Charges	0.6	0.1	1.8	1.8
Impairment and Other	(3.8)	0.1	(4.3)	(1.2)
Total	0.2	7.0	6.9	22.3
Total Operating Segments | Marketing Solutions
Restructuring Cost And Reserve [Line Items]
Employee Terminations	(0.2)	2.2	0.3	4.3
Other Restructuring Charges	1.2	1.3	4.7	1.8
Multi-Employer Pension Plan Charges	0.1	0.1	0.3	0.3
Impairment and Other		1.1	0.5	1.1
Total	1.1	4.7	5.8	7.5
Corporate
Restructuring Cost And Reserve [Line Items]
Employee Terminations	0.5	2.2	2.4	8.9
Other Restructuring Charges	2.1	3.2	5.6	18.0
Multi-Employer Pension Plan Charges	0.1	37.1	(1.2)	37.1
Total	$ 2.7	$ 42.5	$ 6.8	$ 64.0