Acquisitions - Additional Information (Detail) - USD ($) $ in Millions		3 Months Ended				12 Months Ended
	Jan. 30, 2014	Dec. 31, 2016	Dec. 31, 2015	Sep. 26, 2015	Jun. 27, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other acquisitions
Payments to Acquire Businesses, Net of Cash Acquired		$ 25.0	$ 0.9		$ 96.0	$ 25.0	$ 1,913.9	$ 12.3
Goodwill		4,217.4	4,259.0			4,217.4	4,259.0	3,230.3
Goodwill, Acquired During Period					43.2	20.8	1,116.4
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		1,031.0	1,061.9			1,031.0	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	1,033.8			$ 1,033.8	$ 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