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Employee Benefit Plans (Details 2) | 12 Months Ended
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Dec. 31, 2014 item | Dec. 31, 2013 | Dec. 31, 2012
Weighted-average assumptions used to determine benefit obligations |  |  |
Discount rate (as a percent) | 3.50%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate | 4.90%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate |
Weighted-average assumptions used to determine net periodic benefit costs |  |  |
Discount rate (as a percent) | 4.90%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate | 4.00%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate |
Original discount rate (as a percent) |  |  | 4.80%wts_DefinedBenefitPlanAssumptionsUsedInCalculatingNetPeriodicBenefitCostOriginalDiscountRate
Long-term rate of return on assets (as a percent) | 6.00%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets | 6.00%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets | 6.50%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets
Guidelines regarding allocation of assets |  |  |
Number of companies or government agencies in which the allocation of assets should not exceed 10% of the total fund | 1 wts_DefinedBenefitPlanTargetAllocationThresholdPercentNumberOfCompaniesOrGovernmentAgencies |  |
Maximum allocation of assets in the securities of any one company or government agency (as a percent) | 10.00%wts_DefinedBenefitPlanTargetAllocationPercentageOfAssetsCompanyOrGovernmentAgencyMaximum |  |
Maximum allocation of assets in any one industry (as a percent) | 20.00%wts_DefinedBenefitPlanTargetAllocationPercentageOfAssetsIndustryMaximum |  |
Number of industries in which the allocation of assets should be no more than 20% of the total fund | 1 wts_DefinedBenefitPlanTargetAllocationThresholdPercentNumberOfIndustries |  |
Individual treasury securities (as a percent) | 50.00%wts_DefinedBenefitPlanTargetAllocationPercentageOfAssetsIndividualTreasurySecurities |  |
Treasury bonds and notes, maximum (as a percent) | 100.00%wts_DefinedBenefitPlanTargetAllocationPercentageOfAssetsTreasuryBondsAndNotesMaximum |  |
Employee Benefit Plans |  |  |
Total (as a percent) | 100.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations | 100.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations |
Equity securities |  |  |
Employee Benefit Plans |  |  |
Total (as a percent) | 4.20%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations / us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis = us-gaap_EquitySecuritiesMember | 9.40%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations / us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis = us-gaap_EquitySecuritiesMember |
Debt securities |  |  |
Employee Benefit Plans |  |  |
Total (as a percent) | 94.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations / us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis = us-gaap_DebtSecuritiesMember | 85.10%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations / us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis = us-gaap_DebtSecuritiesMember |
Other investments |  |  |
Employee Benefit Plans |  |  |
Total (as a percent) | 1.80%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations / us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis = wts_OtherInvestmentMember | 5.50%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations / us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis = wts_OtherInvestmentMember |
Fixed income securities |  |  |
Employee Benefit Plans |  |  |
Total (as a percent) | 95.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations / us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis = us-gaap_FixedIncomeFundsMember |  |
Equity securities and other investments |  |  |
Employee Benefit Plans |  |  |
Total (as a percent) | 5.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations / us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis = wts_EquitySecuritiesAndOtherMember |  |

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- Definition The interest rate used to adjust for the time value of money for the plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(1) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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- Definition The interest rate used to adjust for the time value of money. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(1) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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- Definition An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Glossary Expected Long-Term Rate of Return on Plan Assets -URI http://asc.fasb.org/extlink&oid=6512013 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(3) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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- Definition Percentage of fair value of investments (categorized by debt securities, equity securities, real estate and other plan assets) to the fair value of plan assets held. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 5 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e2446-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(1) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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- Definition The original interest rate (before revision) used to adjust for the time value of money. + References No definition available. + Details
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- Definition Represents the target allocation maximum percentage of investments in the securities of any one company or government agency to total plan assets. + References No definition available. + Details
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- Definition Represents the target allocation percentage of investments in individual treasury securities to total plan assets. + References No definition available. + Details
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