Name:	us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

This element represents total gains or losses for the period (realized and unrealized), arising from assets measured at fair value on a recurring basis using unobservable inputs (Level 3), which are included in earnings or resulted in a change in net asset value.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 32

-Subparagraph c(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

This element represents total gains or losses for the period (realized and unrealized), arising from assets measured at fair value on a recurring basis using unobservable inputs (Level 3), which are included in other comprehensive income (a separate component of shareholders' equity).

+ References

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncome
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

This element represents purchases, sales, issuances, and settlements (net) which have taken place during the period in relation to assets measured at fair value on a recurring basis using unobservable inputs (Level 3).

+ References

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchasesSalesIssuancesSettlements
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

This element represents an asset measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 32

-Subparagraph c

-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 FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the maximum remaining maturity period at date of purchase of instruments considered as cash equivalents.

+ References

No definition available.

+ Details

Name:	wts_CashEquivalentsMaturityPeriodMaximum
Namespace Prefix:	wts_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the amount of contingent liability related to acquisition in case of complete achievement of performance metrics.

+ References

No definition available.

+ Details

Name:	wts_ContingentLiabilityIfPerformanceMetricsAchieved
Namespace Prefix:	wts_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the amount of contingent liability related to acquisition in case of failure to meet the performance metrics.

+ References

No definition available.

+ Details

Name:	wts_ContingentLiabilityIfPerformanceMetricsFailed
Namespace Prefix:	wts_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the minimum remaining maturity period at date of purchase for certificates of deposit classified as short-term investments.

+ References

No definition available.

+ Details

Name:	wts_ShortTermInvestmentSecuritiesCertificatesOfDepositMaturityPeriodMinimum
Namespace Prefix:	wts_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Financial Instruments and Derivative Instruments (Details 2) In Millions, unless otherwise specified	6 Months Ended				6 Months Ended
	Jul. 01, 2012 M	Jul. 01, 2012 BRAE USD ($)	Jul. 01, 2012 Tekmar USD ($)	Jul. 01, 2012 Tekmar CAD	Jul. 01, 2012 Contingent consideration USD ($)	Dec. 31, 2010 Contingent consideration USD ($)
Reconciliation of changes in fair value of all financial assets and liabilities
Balance at the beginning of the period					$ 1.1	$ 1.9
Purchases, sales, settlements, net					5.1
Total realized and unrealized (gains) losses included in Earnings					0.1
Total realized and unrealized (gains) losses included in Comprehensive income					(0.2)
Balance at the ending of the period					6.1	1.9
Contingent liability in case of failure to meet the performance metrics		0	0
Contingent liability in case of complete achievement of performance metrics		$ 4.8		8.2
Short-term investments, minimum maturity period for certificates of deposit (in months)	3
Cash equivalent instruments remaining maturities (in months)	3