Quarterly Financial Information (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2011		Oct. 01, 2011		Jul. 02, 2011		Apr. 02, 2011		Dec. 31, 2010		Oct. 02, 2010		Jul. 03, 2010		Apr. 03, 2010		Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Quarterly Financial Information [Line Items]
Net sales	$ 865,692		$ 890,546		$ 910,175		$ 790,273		$ 753,858		$ 773,735		$ 796,167		$ 707,013		$ 3,456,686		$ 3,030,773		$ 2,692,468
Gross profit	264,865		272,062		287,736		249,059		232,228		236,542		248,168		213,702		1,073,722		930,640		785,135
Operating income	(119,985)		92,903		109,422		86,177		79,605		90,823		100,126		63,601		168,517		334,155		219,948
Income from continuing operations	(133,704)		52,054		68,137		52,034		49,577		55,729		61,612		36,029		38,521		202,947		116,219
Gain (loss) on disposal of discontinued operations, net of tax									(2,292)		549		593		524				(626)		(19)
Net income from continuing operations attributable to Pentair, Inc.	$ (134,123)		$ 51,092		$ 66,712		$ 50,541		$ 48,668		$ 54,501		$ 60,488		$ 34,797		$ 34,222		$ 198,454		$ 115,512
Basic
Continuing operations	$ (1.36)	[1]	$ 0.52	[1]	$ 0.68	[1]	$ 0.52	[1]	$ 0.50	[1]	$ 0.55	[1]	$ 0.61	[1]	$ 0.35	[1]	$ 0.35	[1]	$ 2.02	[1]	$ 1.19
Discontinued operations									$ (0.02)	[1]	$ 0.01	[1]	$ 0.01	[1]	$ 0.01	[1]			$ (0.01)	[1]
Basic earnings per common share	$ (1.36)	[1]	$ 0.52	[1]	$ 0.68	[1]	$ 0.52	[1]	$ 0.48	[1]	$ 0.56	[1]	$ 0.62	[1]	$ 0.36	[1]	$ 0.35	[1]	$ 2.01	[1]	$ 1.19
Diluted
Continuing operations	$ (1.36)	[1]	$ 0.51	[1]	$ 0.67	[1]	$ 0.51	[1]	$ 0.49	[1]	$ 0.55	[1]	$ 0.61	[1]	$ 0.35	[1]	$ 0.34	[1]	$ 2.00	[1]	$ 1.17
Discontinued operations									$ (0.02)	[1]					$ 0.01	[1]			$ (0.01)	[1]
Diluted earnings per common share	$ (1.36)	[1]	$ 0.51	[1]	$ 0.67	[1]	$ 0.51	[1]	$ 0.47	[1]	$ 0.55	[1]	$ 0.61	[1]	$ 0.36	[1]	$ 0.34	[1]	$ 1.99	[1]	$ 1.17

[1] Amounts may not total to annual earnings because each quarter and year are calculated separately based on basic and diluted weighted-average common shares outstanding during that period.