Debt (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
Oct. 02, 2011 year
Credit Agreement
Credit Agreement
Multi-currency borrowing capacity	$ 300.0
Term of senior unsecured revolving credit facility (in years)	5
Potential additional borrowing capacity	150.0
Sublimit on letters of credit	75.0
Unused and available credit under the credit agreement	198.8
Stand-by letters of credit outstanding	34.6
Eurocurrency rate loans
Credit Agreement
Interest rate, variable rate basis	LIBOR
Interest rate added to base rate, low end of range (as a percent)	1.70%
Interest rate added to base rate, high end of range (as a percent)	2.30%
Euro-based borrowings outstanding under the credit agreement	$ 66.6
Base rate loans and swing line loans
Credit Agreement
Interest rate, variable rate basis	the highest of (a) the federal funds rate plus 0.5%, (b) the rate of interest in effect for such day as announced by Bank of America, N.A. as its "prime rate," and (c) the British Bankers Association LIBOR rate plus 1.0%
Interest rate added to base rate, low end of range (as a percent)	0.70%
Interest rate added to base rate, high end of range (as a percent)	1.30%
Base rate loans and swing line loans \| LIBOR
Credit Agreement
Interest rate, variable rate basis	LIBOR
Interest rate added to base rate (as a percent)	1.00%
Base rate loans and swing line loans \| Federal funds
Credit Agreement
Interest rate, variable rate basis	federal funds rate
Interest rate added to base rate (as a percent)	0.50%

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

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Period Type:	duration

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ Details

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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 20, 22

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The percentage points added to the specified reference rate to compute the variable rate on the debt instrument, in addition to the percentage points added regardless of specified reference rate.

+ Details

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Namespace Prefix:	wts
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The high end of the range of percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ Details

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Namespace Prefix:	wts
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The low end of the range of percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ Details

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Namespace Prefix:	wts
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the maximum amount of the guarantees available through letters of credit.

+ Details

Name:	wts_LettersOfCreditMaximumAmount
Namespace Prefix:	wts
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the additional amount of borrowing capacity that may be added under the credit facility.

+ Details

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Namespace Prefix:	wts
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the term of the unsecured revolving credit facility.

+ Details

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Namespace Prefix:	wts
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration