Financial Instruments and Derivative Instruments (Details 3)	9 Months Ended
Sep. 27, 2015
Derivative instruments
Percentage of projected intercompany purchases hedged by forward exchange contracts	50.00%
Period of projected intercompany purchase transactions	12 months

Represents the percentage of projected intercompany purchase transactions hedged for the next twelve months by forward exchange contracts.

No definition available.

Name:	wts_PercentageOfProjectedIntercompanyPurchaseTransactionsHedgedForNextTwelveMonthsByForwardExchangeContracts
Namespace Prefix:	wts_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration