Pro Forma Information (Detail) (USD $) In Thousands, except Per Share data	3 Months Ended	6 Months Ended
Jul. 02, 2011	Jul. 03, 2010	Jul. 02, 2011	Jul. 03, 2010
Weighted average common shares outstanding
Basic	98,333	98,208	98,190	98,081
Diluted	100,065	99,638	99,825	99,435
Business Acquisition Pro Forma Information
Business Acquisition [Line Items]
Pro forma net sales from continuing operations	$ 953,375	$ 866,193	$ 1,822,224	$ 1,646,945
Pro forma income from continuing operations	66,075	59,536	115,517	92,977
Income (loss) from discontinued operations, net of tax		593		1,117
Pro forma net income from continuing operations attributable to Pentair, Inc.	$ 64,650	$ 58,412	$ 112,599	$ 90,621
Pro forma earnings per common share - continuing operations
Basic	$ 0.66	$ 0.59	$ 1.15	$ 0.92
Diluted	$ 0.65	$ 0.59	$ 1.13	$ 0.91
Weighted average common shares outstanding
Basic	98,333	98,208	98,190	98,081
Diluted	100,065	99,638	99,825	99,435

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