Acquisitions - Additional Information (Detail) - USD ($) $ in Millions		3 Months Ended				12 Months Ended
	Jan. 30, 2014	Dec. 31, 2015	Sep. 26, 2015	Jun. 27, 2015	Mar. 29, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other acquisitions
Payments to Acquire Businesses, Net of Cash Acquired		$ 0.9		$ 96.0		$ 1,913.9	$ 12.3	$ 92.4
Goodwill		5,255.4				5,255.4	4,741.9	$ 4,860.7
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual						147.0
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual							12.7
Goodwill, Acquired During Period				43.2		1,116.4	6.8
Finite-lived Intangible Assets Acquired				53.3
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests							$ 134.7
ERICO Global Company [Member]
Other acquisitions
Payments to Acquire Businesses, Net of Cash Acquired			$ 1,800.0
Goodwill		1,061.9	1,102.8			1,061.9
Indefinite-lived Intangible Assets Acquired			228.4
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill		1,033.8	964.6			$ 1,033.8
Finite-lived Intangible Assets Acquired			$ 805.4
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			21 years
Pentair Residential Filtration [Member]
Other acquisitions
Percentage Of Ownership Interest Acquired	19.90%
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests					$ 134.3
Percentage of ownership interests before acquisition	80.10%
Canada, Dollars
Other acquisitions
Payments to Acquire Businesses, Net of Cash Acquired		$ 1.2		$ 120.5