Earnings Per Share - Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 26, 2015	Sep. 27, 2014	Sep. 26, 2015	Sep. 27, 2014
Computation Of Earnings Per Share Line Items
Net income	$ 115.2	$ (186.0)	$ 376.9	$ 94.1
Income (Loss) from Continuing Operations Attributable to Parent	$ 115.2	$ 192.5	$ 387.3	$ 477.2
Weighted average common shares outstanding
Basic (shares)	180.2	190.2	180.1	193.2
Dilutive impact of stock options and restricted stock units (shares)	2.4	2.9	2.5	3.2
Diluted (shares)	182.6	193.1	182.6	196.4
Earnings per common share attributable to Pentair plc
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.64	$ 1.01	$ 2.15	$ 2.47
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	0.00	(1.99)	(0.06)	(1.98)
Basic (USD per share)	0.64	(0.98)	2.09	0.49
Income (Loss) from Continuing Operations, Per Diluted Share	0.63	1.00	2.12	2.43
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	0.00	(1.95)	(0.06)	(1.95)
Diluted (USD per share)	$ 0.63	$ (0.95)	$ 2.06	$ 0.48
Anti-dilutive stock options excluded from the calculation of diluted earnings per share	1.2	0.5	1.2	0.5