Supplemental Guarantor Information - Condensed Consolidating Balance Sheet (Detail) - USD ($) $ in Millions	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Current assets
Cash and cash equivalents	$ 113.2			$ 74.3	$ 64.7			$ 86.3
Accounts and notes receivable, net	404.0			488.2
Inventories	390.3			387.5
Other current assets	95.1			89.4
Total current assets	1,002.6			1,039.4
Property, plant and equipment, net	277.9			272.6
Other assets
Investments in subsidiaries	0.0			0.0
Goodwill	2,261.0			2,072.7
Intangibles, net	341.4			276.3
Other non-current assets	197.5			145.5
Total other assets	2,799.9			2,494.5
Total assets	4,080.4			3,806.5
Current liabilities
Accounts payable	253.4			378.6
Employee compensation and benefits	70.7			111.7
Other current liabilities	370.1			328.4
Total current liabilities	694.2			818.7
Other liabilities
Long-term debt	1,118.7			787.6
Pension and other post-retirement compensation and benefits	88.1			90.0
Deferred tax liabilities	111.4			105.9
Other non-current liabilities	199.2			168.2
Total liabilities	2,211.6			1,970.4
Equity
Total equity	1,868.8	$ 1,806.6	$ 1,870.4	1,836.1	1,880.2	$ 1,888.9	$ 4,719.7	5,037.8
Total liabilities and equity	4,080.4			3,806.5
Parent Company Guarantor
Current assets
Cash and cash equivalents	0.1			0.1	0.1			0.0
Accounts and notes receivable, net	10.7			4.6
Inventories	0.0			0.0
Other current assets	0.6			3.4
Total current assets	11.4			8.1
Property, plant and equipment, net	0.0			0.0
Other assets
Investments in subsidiaries	2,072.2			1,903.8
Goodwill	0.0			0.0
Intangibles, net	0.0			0.0
Other non-current assets	13.3			23.3
Total other assets	2,085.5			1,927.1
Total assets	2,096.9			1,935.2
Current liabilities
Accounts payable	3.3			0.9
Employee compensation and benefits	0.2			0.2
Other current liabilities	33.6			47.6
Total current liabilities	37.1			48.7
Other liabilities
Long-term debt	170.5			29.9
Pension and other post-retirement compensation and benefits	0.0			0.0
Deferred tax liabilities	0.0			0.0
Other non-current liabilities	20.5			20.5
Total liabilities	228.1			99.1
Equity
Total equity	1,868.8			1,836.1
Total liabilities and equity	2,096.9			1,935.2
Guarantor Subsidiaries
Current assets
Cash and cash equivalents	0.0			0.0	0.0			0.0
Accounts and notes receivable, net	0.0			0.0
Inventories	0.0			0.0
Other current assets	0.0			0.0
Total current assets	0.0			0.0
Property, plant and equipment, net	0.0			0.0
Other assets
Investments in subsidiaries	2,071.6			2,036.1
Goodwill	0.0			0.0
Intangibles, net	0.0			0.0
Other non-current assets	1.0			0.0
Total other assets	2,072.6			2,036.1
Total assets	2,072.6			2,036.1
Current liabilities
Accounts payable	0.1			0.0
Employee compensation and benefits	0.0			0.0
Other current liabilities	0.3			1.5
Total current liabilities	0.4			1.5
Other liabilities
Long-term debt	0.0			130.8
Pension and other post-retirement compensation and benefits	0.0			0.0
Deferred tax liabilities	0.0			0.0
Other non-current liabilities	0.0			0.0
Total liabilities	0.4			132.3
Equity
Total equity	2,072.2			1,903.8
Total liabilities and equity	2,072.6			2,036.1
Subsidiary Issuer
Current assets
Cash and cash equivalents	0.1			0.1	0.1			0.0
Accounts and notes receivable, net	7.1			0.0
Inventories	0.0			0.0
Other current assets	0.0			2.2
Total current assets	7.2			2.3
Property, plant and equipment, net	0.0			0.0
Other assets
Investments in subsidiaries	2,825.6			2,675.7
Goodwill	0.0			0.0
Intangibles, net	0.0			0.0
Other non-current assets	1,272.3			696.1
Total other assets	4,097.9			3,371.8
Total assets	4,105.1			3,374.1
Current liabilities
Accounts payable	0.0			0.0
Employee compensation and benefits	0.0			0.0
Other current liabilities	9.4			4.4
Total current liabilities	9.4			4.4
Other liabilities
Long-term debt	2,024.3			1,333.9
Pension and other post-retirement compensation and benefits	0.0			0.0
Deferred tax liabilities	0.0			0.0
Other non-current liabilities	0.0			0.0
Total liabilities	2,033.7			1,338.3
Equity
Total equity	2,071.4			2,035.8
Total liabilities and equity	4,105.1			3,374.1
Non-Guarantor Subsidiaries
Current assets
Cash and cash equivalents	113.0			74.1	64.5			86.3
Accounts and notes receivable, net	390.3			483.6
Inventories	390.3			387.5
Other current assets	94.5			99.2
Total current assets	988.1			1,044.4
Property, plant and equipment, net	277.9			272.6
Other assets
Investments in subsidiaries	0.0			0.0
Goodwill	2,261.0			2,072.7
Intangibles, net	341.4			276.3
Other non-current assets	184.2			729.7
Total other assets	2,786.6			3,078.7
Total assets	4,052.6			4,395.7
Current liabilities
Accounts payable	254.1			377.7
Employee compensation and benefits	70.5			111.5
Other current liabilities	326.8			290.3
Total current liabilities	651.4			779.5
Other liabilities
Long-term debt	197.2			596.6
Pension and other post-retirement compensation and benefits	88.1			90.0
Deferred tax liabilities	111.4			105.9
Other non-current liabilities	178.7			147.7
Total liabilities	1,226.8			1,719.7
Equity
Total equity	2,825.8			2,676.0
Total liabilities and equity	4,052.6			4,395.7
Consolidation, Eliminations
Current assets
Cash and cash equivalents	0.0			0.0	$ 0.0			$ 0.0
Accounts and notes receivable, net	(4.1)			0.0
Inventories	0.0			0.0
Other current assets	0.0			(15.4)
Total current assets	(4.1)			(15.4)
Property, plant and equipment, net	0.0			0.0
Other assets
Investments in subsidiaries	(6,969.4)			(6,615.6)
Goodwill	0.0			0.0
Intangibles, net	0.0			0.0
Other non-current assets	(1,273.3)			(1,303.6)
Total other assets	(8,242.7)			(7,919.2)
Total assets	(8,246.8)			(7,934.6)
Current liabilities
Accounts payable	(4.1)			0.0
Employee compensation and benefits	0.0			0.0
Other current liabilities	0.0			(15.4)
Total current liabilities	(4.1)			(15.4)
Other liabilities
Long-term debt	(1,273.3)			(1,303.6)
Pension and other post-retirement compensation and benefits	0.0			0.0
Deferred tax liabilities	0.0			0.0
Other non-current liabilities	0.0			0.0
Total liabilities	(1,277.4)			(1,319.0)
Equity
Total equity	(6,969.4)			(6,615.6)
Total liabilities and equity	$ (8,246.8)			$ (7,934.6)