Financial Statements of Parent Company Guarantor - Condensed Consolidating Statement of Operations and Comprehensive Income (Loss) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 28, 2015	Sep. 27, 2014	Mar. 29, 2014
Condensed Financial Statements, Captions [Line Items]
Net sales	$ 1,475.0		$ 1,644.0
Cost of goods sold	964.8		1,079.9
Gross profit	510.2		564.1
Selling, general and administrative	309.2		352.5
Research and development	29.8		29.5
Operating Income (Loss)	171.2		182.1
Income (Loss) from Equity Method Investments	(0.5)		(0.3)
Other (income) expense:
Net interest expense	18.2		16.1
Income before income taxes and noncontrolling interest	153.5		166.3
Provision for income taxes	35.3		40.8
Net Income (Loss) from Continuing Operations	118.2		125.5
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	4.3		1.3
Discontinued Operation, Provision for Loss (Gain) on Disposal, Net of Tax	0	(380.1)	(5.6)
Net income (loss) attributable to Pentair plc	113.9		118.6
Income (Loss) from Continuing Operations Attributable to Parent	118.2		125.5
Comprehensive income (loss), net of tax
Net income	113.9		118.6
Changes in cumulative translation adjustment	174.2		27.9
Changes in market value of derivative financial instruments	(0.1)		0.2
Comprehensive income (loss) attributable to Pentair plc	(60.4)		90.9
Parent Company Guarantor
Condensed Financial Statements, Captions [Line Items]
Selling, general and administrative	3.1		(0.3)
Operating Income (Loss)	(3.1)		0.3
Other (income) expense:
Net interest expense	0		0.3
Income before income taxes and noncontrolling interest	117.6		125.5
Provision for income taxes	(0.6)		0
Net Income (Loss) from Continuing Operations	118.2		125.5
Net income (loss) attributable to Pentair plc	113.9		118.6
Comprehensive income (loss), net of tax
Net income	113.9		118.6
Changes in cumulative translation adjustment	174.2		27.9
Changes in market value of derivative financial instruments	(0.1)		0.2
Comprehensive income (loss) attributable to Pentair plc	(60.4)		90.9
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Selling, general and administrative	0.1
Operating Income (Loss)	(0.1)
Other (income) expense:
Net interest expense	0.9
Income before income taxes and noncontrolling interest	120.7
Provision for income taxes	0
Net Income (Loss) from Continuing Operations	120.7
Net income (loss) attributable to Pentair plc	116.4
Comprehensive income (loss), net of tax
Net income	116.4
Changes in cumulative translation adjustment	174.2
Changes in market value of derivative financial instruments	(0.1)
Comprehensive income (loss) attributable to Pentair plc	(57.9)
Subsidiary Issuer
Condensed Financial Statements, Captions [Line Items]
Selling, general and administrative	1.1		3.3
Operating Income (Loss)	(1.1)		(3.3)
Other (income) expense:
Net interest expense	3.5		0.9
Income before income taxes and noncontrolling interest	113.9		129.8
Provision for income taxes	0		0
Net Income (Loss) from Continuing Operations	113.9		129.8
Net income (loss) attributable to Pentair plc	109.6		122.9
Comprehensive income (loss), net of tax
Net income	109.6		122.9
Changes in cumulative translation adjustment	174.2		27.9
Changes in market value of derivative financial instruments	(0.1)		0.2
Comprehensive income (loss) attributable to Pentair plc	(64.7)		95.2
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net sales	1,475.0		1,644.0
Cost of goods sold	964.8		1,079.9
Gross profit	510.2		564.1
Selling, general and administrative	304.9		349.5
Research and development	29.8		29.5
Operating Income (Loss)	175.5		185.1
Income (Loss) from Equity Method Investments	(0.5)		(0.3)
Other (income) expense:
Net interest expense	13.8		14.9
Income before income taxes and noncontrolling interest	162.2		170.5
Provision for income taxes	35.9		40.8
Net Income (Loss) from Continuing Operations	126.3		129.7
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	4.3		1.3
Discontinued Operation, Provision for Loss (Gain) on Disposal, Net of Tax			5.6
Net income (loss) attributable to Pentair plc	122.0		122.8
Comprehensive income (loss), net of tax
Net income	122.0		122.8
Changes in cumulative translation adjustment	174.2		27.9
Changes in market value of derivative financial instruments	(0.1)		0.2
Comprehensive income (loss) attributable to Pentair plc	(52.3)		95.1
Eliminations
Other (income) expense:
Income before income taxes and noncontrolling interest	(360.9)		259.5
Net Income (Loss) from Continuing Operations	(360.9)		(259.5)
Net income (loss) attributable to Pentair plc	(348.0)		(245.7)
Comprehensive income (loss), net of tax
Net income	(348.0)		(245.7)
Changes in cumulative translation adjustment	(522.6)		(55.8)
Changes in market value of derivative financial instruments	0.3		(0.4)
Comprehensive income (loss) attributable to Pentair plc	174.9		(190.3)
Continuing Operations [Member] | Parent Company Guarantor
Condensed Financial Statements, Captions [Line Items]
Loss (earnings) from investment in subsidiaries	(120.7)		(125.5)
Continuing Operations [Member] | Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Loss (earnings) from investment in subsidiaries	(121.7)
Continuing Operations [Member] | Subsidiary Issuer
Condensed Financial Statements, Captions [Line Items]
Loss (earnings) from investment in subsidiaries	(118.5)		(134.0)
Continuing Operations [Member] | Eliminations
Condensed Financial Statements, Captions [Line Items]
Loss (earnings) from investment in subsidiaries	360.9		259.5
Discontinued Operations [Member] | Parent Company Guarantor
Condensed Financial Statements, Captions [Line Items]
Loss (earnings) from investment in subsidiaries	(4.3)		(6.9)
Discontinued Operations [Member] | Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Loss (earnings) from investment in subsidiaries	(4.3)
Discontinued Operations [Member] | Subsidiary Issuer
Condensed Financial Statements, Captions [Line Items]
Loss (earnings) from investment in subsidiaries	(4.3)		(6.9)
Discontinued Operations [Member] | Eliminations
Condensed Financial Statements, Captions [Line Items]
Loss (earnings) from investment in subsidiaries	$ 12.9		$ 13.8