Goodwill and Intangibles - Intangibles (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
	Nov. 02, 2016	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Intangible assets subject to amortization
Gross Carrying Amount		$ 335.6	$ 335.6	$ 332.6
Accumulated Amortization		(187.7)	(187.7)	(165.4)
Net Carrying Amount		147.9	147.9	167.2
Indefinite-lived intangible assets
Indefinite-lived intangible assets		37.3	37.3	35.3
Intangible assets
Gross Carrying Amount		372.9	372.9	367.9
Net Carrying Amount		185.2	185.2	202.5
Indefinite-lived intangible asset impairment			$ 0.4	0.6
Estimated useful lives			12 years 6 months
Aggregate amortization expense for amortized intangible assets			$ 22.5	20.8	$ 20.9
Amortization expense
2018		19.5	19.5
2019		15.5	15.5
2020		15.0	15.0
2021		13.3	13.3
2022		11.6	11.6
Patents
Intangible assets subject to amortization
Gross Carrying Amount		16.1	16.1	16.1
Accumulated Amortization		(15.4)	(15.4)	(14.9)
Net Carrying Amount		0.7	$ 0.7	1.2
Intangible assets
Estimated useful lives			3 years 3 months 18 days
Customer relationships
Intangible assets subject to amortization
Gross Carrying Amount		233.2	$ 233.2	231.5
Accumulated Amortization		(133.5)	(133.5)	(117.3)
Net Carrying Amount		99.7	$ 99.7	114.2
Intangible assets
Estimated useful lives			11 years 3 months 18 days
Technology
Intangible assets subject to amortization
Gross Carrying Amount		53.9	$ 53.9	53.1
Accumulated Amortization		(23.1)	(23.1)	(19.2)
Net Carrying Amount		30.8	$ 30.8	33.9
Intangible assets
Estimated useful lives			8 years 1 month 6 days
Trade name
Intangible assets subject to amortization
Gross Carrying Amount		25.5	$ 25.5	25.1
Accumulated Amortization		(9.7)	(9.7)	(8.1)
Net Carrying Amount		15.8	$ 15.8	17.0
Intangible assets
Estimated useful lives			14 years 4 months 24 days
Other
Intangible assets subject to amortization
Gross Carrying Amount		6.9	$ 6.9	6.8
Accumulated Amortization		(6.0)	(6.0)	(5.9)
Net Carrying Amount		0.9	$ 0.9	0.9
Intangible assets
Estimated useful lives			19 years 8 months 12 days
Americas | Technology
Intangible assets
Finite-lived intangible asset impairment		1.0
PVI Riverside Holdings, Inc Member
Intangible assets
Net Carrying Amount		31.0	$ 31.0
Estimated useful lives			16 years 1 month 6 days
PVI Riverside Holdings, Inc Member | Customer relationships
Intangible assets
Net Carrying Amount		17.6	$ 17.6
Estimated useful lives	15 years		15 years
PVI Riverside Holdings, Inc Member | Technology
Intangible assets
Net Carrying Amount		10.2	$ 10.2
Estimated useful lives	10 years		10 years
PVI Riverside Holdings, Inc Member | Trade name
Intangible assets
Gross Carrying Amount		$ 3.2	$ 3.2
Estimated useful lives	20 years		20 years
Watts Korea | Customer relationships
Intangible assets
Net Carrying Amount				$ 1.6
Estimated useful lives				10 years
Europe | Trade name
Intangible assets
Indefinite-lived intangible asset impairment				$ 0.4
Europe | Europe | Trade name
Intangible assets
Indefinite-lived intangible asset impairment					0.1
Americas | Trade name
Intangible assets
Indefinite-lived intangible asset impairment					$ 0.5