Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2011	Jul. 02, 2011
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2011
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	FY
Trading Symbol	PNR
Entity Registrant Name	PENTAIR INC
Entity Central Index Key	0000077360
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding	98,622,564
Entity Public Float		$ 3,886,388,296