Segment and Related Information - Summary of Financial Information Concerning Reportable Segments (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Service revenues	$ 400.4	$ 419.5	$ 419.1	$ 384.0	$ 394.8	$ 400.6	$ 398.1	$ 364.7	$ 1,623.0	$ 1,558.2	$ 1,507.6
Operating Income (Loss)	18.4	$ 29.5	$ 8.7	$ 17.9	29.2	$ 17.5	$ 35.0	$ 20.0	74.5	101.7	90.1
Depreciation and Amortization									278.8	270.5	269.8
Capital Expenditures									203.8	188.6	186.6
Total Assets	3,543.5				3,528.3				3,543.5	3,528.3	3,493.3
Operating Segments | South
Segment Reporting Information [Line Items]
Service revenues									645.6	609.2	570.5
Operating Income (Loss)									77.6	77.9	89.8
Depreciation and Amortization									93.9	85.1	85.0
Capital Expenditures									90.3	70.1	65.0
Total Assets	1,301.9				1,261.4				1,301.9	1,261.4	1,219.7
Operating Segments | East
Segment Reporting Information [Line Items]
Service revenues									415.0	400.5	380.2
Operating Income (Loss)									21.6	22.5	(1.5)
Depreciation and Amortization									82.4	79.8	76.8
Capital Expenditures									51.6	59.4	57.0
Total Assets	819.7				837.4				819.7	837.4	837.6
Operating Segments | Midwest
Segment Reporting Information [Line Items]
Service revenues									562.4	548.5	556.9
Operating Income (Loss)									66.4	72.7	71.7
Depreciation and Amortization									97.2	101.1	98.9
Capital Expenditures									54.0	54.1	62.7
Total Assets	1,367.6				1,379.9				1,367.6	1,379.9	1,400.2
Corporate
Segment Reporting Information [Line Items]
Service revenues									0.0	0.0	0.0
Operating Income (Loss)									(91.1)	(71.4)	(69.9)
Depreciation and Amortization									5.3	4.5	9.1
Capital Expenditures									7.9	5.0	1.9
Total Assets	$ 54.3				$ 49.6				$ 54.3	$ 49.6	$ 35.8