Leases - Narrative (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Operating lease costs	$ 3.9	$ 3.5
Amortization of right-of-use assets	0.4	0.4
Interest on lease liabilities	0.5	0.5
Variable lease costs	0.4	0.2
Total lease costs	5.2	4.6
Operating cash flows from operating leases	4.4	4.1
Operating cash flows from finance leases	0.5	0.5
Financing cash flows from finance leases	0.3	0.3
Non-cash amounts for lease liabilities arising from obtaining right-of-use assets, operating leases	0.6	0.1
Non-cash amounts for lease liabilities arising from obtaining right-of-use assets, finance leases	0.3	0.5
Operating lease right-of-use assets	70.4		$ 73.1
Finance lease assets	26.7		26.5
Total lease ROU assets	1,896.8		1,877.7
Current operating lease liabilities	14.0		13.9
Current finance lease liabilities	1.6		1.4
Liabilities, Current	290.4		280.4
Non-current operating lease liabilities	62.7		65.6
Non-current finance lease liabilities	20.4		20.6
Total lease liabilities	76.7		79.5
Finance Lease, Liability	22.0		22.0
TOTAL LIABILITIES	1,452.1		1,445.7
Lease assets [Member]
Capital Leases, Lessee Balance Sheet, Assets by Major Class, Accumulated Depreciation	(11.4)		(11.1)
Total lease ROU assets	85.7		88.5
Lease liabilities, current [Member]
Liabilities, Current	15.6		15.3
Lease liabilities, noncurrent [Member]
Liabilities, Noncurrent	83.0		86.2
Lease liabilities [Member]
TOTAL LIABILITIES	98.6		$ 101.5
Finance lease costs [Member]
Total lease costs	$ 0.9	$ 0.9
Minimum
Remaining lease term	1 year
Maximum
Remaining lease term	12 years