Financial Statements of Parent Company Guarantor - Condensed Consolidating Statement of Operations and Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 27, 2015	Sep. 27, 2014	Jun. 28, 2014	Jun. 27, 2015	Jun. 28, 2014
Condensed Financial Statements, Captions [Line Items]
Net sales	$ 1,661.2		$ 1,834.1	$ 3,136.2	$ 3,478.1
Cost of goods sold	1,095.0		1,187.8	2,059.8	2,267.7
Gross profit	566.2		646.3	1,076.4	1,210.4
Selling, general and administrative	319.3		389.7	628.5	742.2
Research and development	29.0		30.2	58.8	59.7
Operating Income (Loss)	217.9		226.4	389.1	408.5
Income (Loss) from Equity Method Investments	(0.6)		(0.3)	(1.1)	(0.6)
Gain (Loss) on Disposition of Business	0.0		(0.2)	0.0	(0.2)
Other (income) expense:
Net interest expense	18.6		17.9	36.8	34.0
Income before income taxes and noncontrolling interest	199.9		208.6	353.4	374.9
Provision for income taxes	46.0		49.4	81.3	90.2
Net Income (Loss) from Continuing Operations	153.9		159.2	272.1	284.7
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	1.3		(2.3)	5.6	(1.0)
Discontinued Operation, Provision for Loss (Gain) on Disposal, Net of Tax	(4.8)	$ (380.1)	0.0	(4.8)	(5.6)
Net income (loss) attributable to Pentair plc	147.8		161.5	261.7	280.1
Income (Loss) from Continuing Operations Attributable to Parent	153.9		159.2	272.1	284.7
Comprehensive income (loss), net of tax
Net income	147.8		161.5	261.7	280.1
Changes in cumulative translation adjustment	(21.6)		(16.4)	152.6	11.5
Changes in market value of derivative financial instruments	(0.8)		0.2	(0.9)	0.4
Comprehensive income (loss) attributable to Pentair plc	168.6		178.1	108.2	269.0
Parent Company Guarantor
Condensed Financial Statements, Captions [Line Items]
Selling, general and administrative	9.5		8.2	12.7	7.9
Operating Income (Loss)	(9.5)		(8.2)	(12.7)	(7.9)
Other (income) expense:
Net interest expense	0.0		0.4	0.0	0.7
Income before income taxes and noncontrolling interest	153.8		159.2	271.4	284.7
Provision for income taxes	(0.1)		0.0	(0.7)	0.0
Net Income (Loss) from Continuing Operations	153.9		159.2	272.1	284.7
Net income (loss) attributable to Pentair plc	147.8		161.5	261.7	280.1
Comprehensive income (loss), net of tax
Net income	147.8		161.5	261.7	280.1
Changes in cumulative translation adjustment	(21.6)		(16.4)	152.6	11.5
Changes in market value of derivative financial instruments	(0.8)		0.2	(0.9)	0.4
Comprehensive income (loss) attributable to Pentair plc	168.6		178.1	108.2	269.0
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Selling, general and administrative	0.0		2.8	0.1	2.8
Operating Income (Loss)	0.0		(2.8)	(0.1)	(2.8)
Other (income) expense:
Net interest expense	0.5		0.3	1.3	0.3
Income before income taxes and noncontrolling interest	163.3		167.8	284.1	174.7
Provision for income taxes	0.0			0.0	0.0
Net Income (Loss) from Continuing Operations	163.3		167.8	284.1	174.7
Net income (loss) attributable to Pentair plc	157.2		170.1	273.7	170.1
Comprehensive income (loss), net of tax
Net income	157.2		170.1	273.7	170.1
Changes in cumulative translation adjustment	(21.6)		(16.4)	152.6	11.5
Changes in market value of derivative financial instruments	(0.8)		0.2	(0.9)	0.4
Comprehensive income (loss) attributable to Pentair plc	178.0		186.7	120.2	159.0
Subsidiary Issuer
Condensed Financial Statements, Captions [Line Items]
Selling, general and administrative	0.9		2.6	1.9	5.9
Operating Income (Loss)	(0.9)		(2.6)	(1.9)	(5.9)
Other (income) expense:
Net interest expense	0.4		0.1	3.9	1.0
Income before income taxes and noncontrolling interest	160.4		141.5	274.4	271.3
Provision for income taxes	0.0		1.0	0.0	1.0
Net Income (Loss) from Continuing Operations	160.4		140.5	274.4	270.3
Net income (loss) attributable to Pentair plc	154.3		142.8	264.0	265.7
Comprehensive income (loss), net of tax
Net income	154.3		142.8	264.0	265.7
Changes in cumulative translation adjustment	(21.6)		(16.4)	152.6	11.5
Changes in market value of derivative financial instruments	(0.8)		0.2	(0.9)	0.4
Comprehensive income (loss) attributable to Pentair plc	175.1		159.4	110.5	254.6
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net sales	1,661.2		1,834.1	3,136.2	3,478.1
Cost of goods sold	1,095.0		1,187.8	2,059.8	2,267.7
Gross profit	566.2		646.3	1,076.4	1,210.4
Selling, general and administrative	308.9		376.1	613.8	725.6
Research and development	29.0		30.2	58.8	59.7
Operating Income (Loss)	228.3		240.0	403.8	425.1
Income (Loss) from Equity Method Investments	(0.6)		(0.3)	(1.1)	(0.6)
Gain (Loss) on Disposition of Business			(0.2)		(0.2)
Other (income) expense:
Net interest expense	17.7		17.1	31.6	32.0
Income before income taxes and noncontrolling interest	211.2		223.0	373.3	393.5
Provision for income taxes	46.1		48.4	82.0	89.2
Net Income (Loss) from Continuing Operations	165.1		174.6	291.3	304.3
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	1.3		(2.3)	5.6	1.0
Discontinued Operation, Provision for Loss (Gain) on Disposal, Net of Tax	(4.8)			(4.8)	5.6
Net income (loss) attributable to Pentair plc	159.0		176.9	280.9	299.7
Comprehensive income (loss), net of tax
Net income	159.0		176.9	280.9	299.7
Changes in cumulative translation adjustment	(21.6)		(16.4)	152.6	11.5
Changes in market value of derivative financial instruments	(0.8)		0.2	(0.9)	0.4
Comprehensive income (loss) attributable to Pentair plc	179.8		193.5	127.4	288.6
Eliminations
Other (income) expense:
Income before income taxes and noncontrolling interest	(488.8)		482.9	(849.8)	749.3
Net Income (Loss) from Continuing Operations	(488.8)		(482.9)	(849.8)	(749.3)
Net income (loss) attributable to Pentair plc	(470.5)		(489.8)	(818.6)	(735.5)
Comprehensive income (loss), net of tax
Net income	(470.5)		(489.8)	(818.6)	735.5
Changes in cumulative translation adjustment	64.8		49.2	(457.8)	34.5
Changes in market value of derivative financial instruments	2.4		(0.6)	2.7	1.2
Comprehensive income (loss) attributable to Pentair plc	(532.9)		(539.6)	(358.1)	702.2
Continuing Operations [Member] | Parent Company Guarantor
Condensed Financial Statements, Captions [Line Items]
Loss (earnings) from investment in subsidiaries	(163.3)		(167.8)	(284.1)	(293.3)
Continuing Operations [Member] | Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Loss (earnings) from investment in subsidiaries	(163.8)		(170.9)	(285.5)	(177.8)
Continuing Operations [Member] | Subsidiary Issuer
Condensed Financial Statements, Captions [Line Items]
Loss (earnings) from investment in subsidiaries	(161.7)		(144.2)	(280.2)	(278.2)
Continuing Operations [Member] | Eliminations
Condensed Financial Statements, Captions [Line Items]
Loss (earnings) from investment in subsidiaries	488.8		482.9	849.8	749.3
Discontinued Operations [Member] | Parent Company Guarantor
Condensed Financial Statements, Captions [Line Items]
Loss (earnings) from investment in subsidiaries	(6.1)		2.3	(10.4)	(4.6)
Discontinued Operations [Member] | Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Loss (earnings) from investment in subsidiaries	(6.1)		2.3	(10.4)	(4.6)
Discontinued Operations [Member] | Subsidiary Issuer
Condensed Financial Statements, Captions [Line Items]
Loss (earnings) from investment in subsidiaries	(6.1)		2.3	(10.4)	(4.6)
Discontinued Operations [Member] | Eliminations
Condensed Financial Statements, Captions [Line Items]
Loss (earnings) from investment in subsidiaries	$ 18.3		$ (6.9)	$ 31.2	$ 13.8