Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Value of equity interests (such as common shares, preferred shares, or partnership interest) issued or issuable to acquire the entity.

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Aggregate number of common shares reserved for future issuance.

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The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Stock-based Compensation - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended			3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended								3 Months Ended	9 Months Ended
	Sep. 29, 2012	Oct. 01, 2011	Sep. 29, 2012	Oct. 01, 2011	Dec. 31, 2011	Sep. 29, 2012 2008 Omnibus Stock Incentive Plan Stock Option	Oct. 01, 2011 2008 Omnibus Stock Incentive Plan Stock Option	Sep. 29, 2012 2008 Omnibus Stock Incentive Plan Stock Option	Oct. 01, 2011 2008 Omnibus Stock Incentive Plan Stock Option	Sep. 29, 2012 2008 Omnibus Stock Incentive Plan Restricted Shares and Restricted Stock Units	Oct. 01, 2011 2008 Omnibus Stock Incentive Plan Restricted Shares and Restricted Stock Units	Sep. 29, 2012 2008 Omnibus Stock Incentive Plan Restricted Shares and Restricted Stock Units	Oct. 01, 2011 2008 Omnibus Stock Incentive Plan Restricted Shares and Restricted Stock Units	Sep. 29, 2012 2008 Omnibus Stock Incentive Plan Restricted Shares and Restricted Stock Units Minimum	Sep. 29, 2012 2008 Omnibus Stock Incentive Plan Restricted Shares and Restricted Stock Units Maximum	Sep. 29, 2012 2012 Stock and Incentive Plan	Sep. 28, 2012 2012 Stock and Incentive Plan	Sep. 29, 2012 2012 Stock and Incentive Plan Active Employees	Sep. 29, 2012 2012 Stock and Incentive Plan Non Employees	Sep. 29, 2012 Pentair Ltd	Sep. 29, 2012 Pentair Ltd
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 18.4	$ 4.2	$ 28.5	$ 14.7		$ 5.6	$ 2.0	$ 9.9	$ 6.7	$ 12.8	$ 2.2	$ 18.6	$ 8.0							$ 13.5	$ 13.5
Vesting period														3 years	4 years
Number of shares authorized for issuance	213,000,000	250,000,000	213,000,000	250,000,000	250,000,000												9,000,000
Business Acquisition Equity Interest Issued																$ 108.9		$ 37.6	$ 71.3
Common shares reserved for issuance																9,000,000
Stock awards, weighted average grant-date fair value			$ 13.18	$ 10.00