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Stock-Based Compensation (Details) (USD $) In Millions, except Share data, unless otherwise specified | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Stock-based compensation |  |  |
Total unrecognized compensation cost related to the unvested awards | $ 20.2 us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized |  |
Total weighted average remaining term of unrecognized compensation costs | 1 year 10 months 24 days |  |
Compensation cost recognized | 8.6 us-gaap_AllocatedShareBasedCompensationExpense | 9.6 us-gaap_AllocatedShareBasedCompensationExpense | 6.6 us-gaap_AllocatedShareBasedCompensationExpense
Selling, general and administrative expenses |  |  |
Stock-based compensation |  |  |
Compensation cost recognized | 8.0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember |  |
Performance Shares |  |  |
Stock-based compensation |  |  |
Vesting period | 3 years |  |
Total unrecognized compensation cost related to the unvested awards | 5.0 us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember |  |
Total weighted average remaining term of unrecognized compensation costs | 2 years |  |
Compensation cost recognized | 0.7 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember |  |
Fair value assumptions |  |  |
Weighted average grant-date fair value (in dollars per share) | $ 57.02 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember |  |
Performance Shares | Class A |  |  |
Weighted Average Intrinsic Value |  |  |
Company's closing Common Stock price (in dollars per share) | $ 63.44 us-gaap_SharePrice / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonClassAMember |  |
Performance Shares | Class A | Minimum |  |  |
Stock-based compensation |  |  |
Percentage of stock options becoming exercisable | 0.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonClassAMember |  |
Performance Shares | Class A | Maximum |  |  |
Stock-based compensation |  |  |
Percentage of stock options becoming exercisable | 200.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonClassAMember |  |
Second Amended and Restated 2004 Stock Incentive Plan |  |  |
Stock-based compensation |  |  |
Number of stock incentive plans | 1 wts_ShareBasedCompensationArrangementByShareBasedPaymentAwardPlanNumber / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member |  |
Second Amended and Restated 2004 Stock Incentive Plan | Class A |  |  |
Stock-based compensation |  |  |
Shares authorized | 1,706,591 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member / us-gaap_StatementClassOfStockAxis = us-gaap_CommonClassAMember |  |
Second Amended and Restated 2004 Stock Incentive Plan | Stock options |  |  |
Stock-based compensation |  |  |
Vesting period | 4 years |  |
Percentage of stock options becoming exercisable | 25.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member |  |
Expiration period | 10 years |  |
Total unrecognized compensation cost related to the unvested awards | 5.6 us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member |  |
Total weighted average remaining term of unrecognized compensation costs | 2 years 2 months 12 days |  |
Compensation cost recognized | 2.6 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | 3.8 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | 2.7 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member
Summary of stock option activity and related information |  |  |
Outstanding at beginning of year (in shares) | 1,029,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | 1,064,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | 1,272,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member
Granted (in shares) | 114,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | 379,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | 415,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member
Cancelled/Forfeitures (in shares) | (306,000)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | (53,000)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | (33,000)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member
Exercised (in shares) | (342,000)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | (361,000)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | (590,000)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member
Outstanding at end of year (in shares) | 495,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | 1,029,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | 1,064,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member
Exercisable at end of year (in shares) | 128,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | 249,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | 360,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member
Weighted Average Exercise Price |  |  |
Outstanding at beginning of year (in dollars per share) | $ 41.66 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | $ 33.37 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | $ 30.43 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member
Granted (in dollars per share) | $ 57.58 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | $ 54.78 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | $ 37.67 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member
Cancelled/Forfeitures (in dollars per share) | $ 44.19 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | $ 36.97 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | $ 31.18 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member
Exercised (in dollars per share) | $ 36.48 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | $ 31.73 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | $ 30.19 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member
Outstanding at end of year (in dollars per share) | $ 47.34 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | $ 41.66 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | $ 33.37 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member
Exercisable at end of year (in dollars per share) | $ 40.04 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | $ 32.35 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | $ 30.91 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member
Weighted Average Intrinsic Value |  |  |
Outstanding at end of year (in dollars per share) | $ 16.10 wts_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValuePerShare / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member |  |
Exercisable at end of year (in dollars per share) | $ 23.40 wts_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableIntrinsicValuePerShare / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member |  |
Aggregate intrinsic values of exercisable options (in dollars) | 3.0 us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1 / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member |  |
Total intrinsic value of options exercised | 8.2 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | 7.4 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | 5.7 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member
Fair value assumptions |  |  |
Expected life | 6 years | 6 years | 6 years
Expected stock price volatility (as a percent) | 37.50%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | 40.30%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | 41.20%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member
Expected dividend yield (as a percent) | 1.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | 1.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | 1.20%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member
Risk-free interest rate (as a percent) | 1.90%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | 1.70%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | 0.90%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member
Weighted average grant-date fair value of stock options (in dollars per share) | $ 20.04 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | $ 20.30 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member | $ 13.49 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member
Second Amended and Restated 2004 Stock Incentive Plan | Stock options | Class A |  |  |
Stock-based compensation |  |  |
Minimum exercise price as percentage of fair market value of common stock on grant date | 100.00%wts_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePriceOfCommonStockPercentMinimum / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member / us-gaap_StatementClassOfStockAxis = us-gaap_CommonClassAMember |  |
Weighted Average Intrinsic Value |  |  |
Company's closing Common Stock price (in dollars per share) | $ 63.44 us-gaap_SharePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member / us-gaap_StatementClassOfStockAxis = us-gaap_CommonClassAMember |  |
Second Amended and Restated 2004 Stock Incentive Plan | Stock options | Grants in 2014 |  |  |
Stock-based compensation |  |  |
Expiration period | 3 years |  |
Vesting rate per year for maximum vesting period | 0.33 wts_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRightsForMaximumVestingPeriod / us-gaap_AwardDateAxis = wts_GrantsIn2014Member / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member |  |
Second Amended and Restated 2004 Stock Incentive Plan | Restricted stock | Maximum |  |  |
Stock-based compensation |  |  |
Vesting period | 3 years |  |
Vesting rate per year for maximum vesting period | 0.33 wts_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRightsForMaximumVestingPeriod / us-gaap_AwardTypeAxis = wts_RestrictedStockAwardMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member / us-gaap_RangeAxis = us-gaap_MaximumMember |  |
Second Amended and Restated 2004 Stock Incentive Plan | Restricted stock | Grants in 2014 | Maximum |  |  |
Stock-based compensation |  |  |
Vesting period | 2 years |  |
Percentage of stock options becoming exercisable | 50.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage / us-gaap_AwardDateAxis = wts_GrantsIn2014Member / us-gaap_AwardTypeAxis = wts_RestrictedStockAwardMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member / us-gaap_RangeAxis = us-gaap_MaximumMember |  |
Second Amended and Restated 2004 Stock Incentive Plan | Deferred shares |  |  |
Stock-based compensation |  |  |
Vesting period | 3 years |  |
Vesting rate per year for maximum vesting period | 0.33 wts_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRightsForMaximumVestingPeriod / us-gaap_AwardTypeAxis = us-gaap_DeferredCompensationShareBasedPaymentsMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member |  |
Second Amended and Restated 2004 Stock Incentive Plan | Deferred shares | Grants in 2014 |  |  |
Stock-based compensation |  |  |
Vesting period | 2 years |  |
Percentage of stock options becoming exercisable | 50.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage / us-gaap_AwardDateAxis = wts_GrantsIn2014Member / us-gaap_AwardTypeAxis = us-gaap_DeferredCompensationShareBasedPaymentsMember / us-gaap_PlanNameAxis = wts_StockIncentivePlan2004Member |  |
Management Stock Purchase Plan | Class A |  |  |
Stock-based compensation |  |  |
Shares available for future grants of new equity awards | 913,526 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant / us-gaap_PlanNameAxis = wts_ManagementStockPurchasePlanMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonClassAMember |  |
Shares authorized | 2,000,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized / us-gaap_PlanNameAxis = wts_ManagementStockPurchasePlanMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonClassAMember |  |
Exercise price as percentage of fair market value of common stock on grant date | 67.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent / us-gaap_PlanNameAxis = wts_ManagementStockPurchasePlanMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonClassAMember |  |
Management Stock Purchase Plan | Restricted stock | Class A |  |  |
Weighted Average Intrinsic Value |  |  |
Company's closing Common Stock price (in dollars per share) | $ 63.44 us-gaap_SharePrice / us-gaap_AwardTypeAxis = wts_RestrictedStockAwardMember / us-gaap_PlanNameAxis = wts_ManagementStockPurchasePlanMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonClassAMember |  |
Management Stock Purchase Plan | Restricted stock units (RSUs) |  |  |
Stock-based compensation |  |  |
Total unrecognized compensation cost related to the unvested awards | 0.6 us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_PlanNameAxis = wts_ManagementStockPurchasePlanMember |  |
Total weighted average remaining term of unrecognized compensation costs | 1 year 4 months 24 days |  |
Compensation cost recognized | $ 0.5 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_PlanNameAxis = wts_ManagementStockPurchasePlanMember | $ 0.7 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_PlanNameAxis = wts_ManagementStockPurchasePlanMember | $ 0.8 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_PlanNameAxis = wts_ManagementStockPurchasePlanMember
Fair value assumptions |  |  |
Expected life | 3 years | 3 years | 3 years
Expected stock price volatility (as a percent) | 31.20%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_PlanNameAxis = wts_ManagementStockPurchasePlanMember | 34.10%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_PlanNameAxis = wts_ManagementStockPurchasePlanMember | 38.30%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_PlanNameAxis = wts_ManagementStockPurchasePlanMember
Expected dividend yield (as a percent) | 0.90%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_PlanNameAxis = wts_ManagementStockPurchasePlanMember | 0.90%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_PlanNameAxis = wts_ManagementStockPurchasePlanMember | 1.10%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_PlanNameAxis = wts_ManagementStockPurchasePlanMember
Risk-free interest rate (as a percent) | 0.70%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_PlanNameAxis = wts_ManagementStockPurchasePlanMember | 0.40%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_PlanNameAxis = wts_ManagementStockPurchasePlanMember | 0.40%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_PlanNameAxis = wts_ManagementStockPurchasePlanMember
Weighted average grant-date fair value (in dollars per share) | $ 22.57 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_PlanNameAxis = wts_ManagementStockPurchasePlanMember | $ 18.05 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_PlanNameAxis = wts_ManagementStockPurchasePlanMember | $ 15.68 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_PlanNameAxis = wts_ManagementStockPurchasePlanMember
Management Stock Purchase Plan | Restricted stock units (RSUs) | Minimum |  |  |
Stock-based compensation |  |  |
Vesting period | 3 years |  |

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- Definition Unrecognized cost of unvested share-based compensation awards. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Percentage of vesting of share-based compensation awards. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(iii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 14.D.2) -URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 14 -Section D -Subsection 2 + Details
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- Definition The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Number of options outstanding, including both vested and non-vested options. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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