2.2.0.25falsefalse20600 - Disclosure - Acquisitions (Policies)truefalsefalse1falsefalseUSDfalsefalse1/1/2010 - 12/31/2010 USD ($) USD ($) / shares $FROM_Jan01_2010_TO_Dec31_2010http://www.sec.gov/CIK0001000697duration2010-01-01T00:00:002010-12-31T00:00:00SharesStandardhttp://www.xbrl.org/2003/instancesharesxbrli0USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170EPSDividehttp://www.xbrl.org/2003/iso4217USDiso4217http://www.xbrl.org/2003/instancesharesxbrli0PureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDUSD$2true0wat_AcquisitionsPoliciesAbstractwatfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringNo definition available.falsefalseAcquisitions (Policies) [Abstract]3false0us-gaap_BusinessCombinationsPolicyus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Effective January 1, 2009, the Company implemented the newly issued accounting standard for business combinations. This standard requires an acquiring company to measure all assets acquired and liabilities assumed, including contingent considerations and all contractual contingencies, at fair value as of the acquisition date. In addition, an acquiring company is required to capitalize IPR&D on its balance sheet at its acquisition date fair value. These IPR&D assets are accounted for as indefinite-lived intangible assets until the underlying project is completed. Once the project is completed, the carrying value of the IPR&D is amortized over the estimated useful life of the asset. If a project becomes impaired or abandoned, the carrying value of the IPR&D is written down to its fair value with the related impairment charge recognized in the period in which the impairment occurs. This accounting standard is applicable to acquisitions completed after January 1, 2009. Previous standards generally required post-acquisition adjustments related to business combination deferred tax asset valuation allowances and liabilities for uncertain tax positions to be recorded as an increase or decrease to goodwill. This new accounting standard does not permit this accounting and generally requires any such changes to be recorded in current period income tax expense. Thus, all changes to valuation allowances and liabilities for uncertain tax positions established in acquisition accounting, whether the business combination was accounted for under previous standards or under the newly issued accounting standard, will be recognized in current period income tax expense.Effective January 1, 2009, the Company implemented the newly issued accounting standard for business combinations. This standard requires an acquiringfalsefalsefalsefalsefalseOtherxbrli:stringItemTypestringDescribes how the entity accounts for completed business combinations (purchase method, acquisition method or combination of entities under common control). The policy description may include a general discussion of the purchase method or acquisition method of accounting (including for example, the treatment accorded contingent consideration, the identification of assets and liabilities, the purchase price allocation process, how the fair values of acquired assets and liabilities are determined) and the entity's specific application thereof. An entity that acquires another entity in a leveraged buyout transaction also should disclose the accounting policy followed by the acquiring entity in determining the basis used to value its interest in the acquired entity, and the rationale for that accounting policy.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 141R -Paragraph 7 -Subparagraph a, b, c, d Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 141 -Paragraph 9, 10, 11, 12, 13 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Emerging Issues Task Force (EITF) -Number 88-16 -Section SEC Observer Comments Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 141R -Paragraph 6 falsefalseBusiness Combinations Policy12Acquisitions (Policies)UnKnownUnKnownUnKnownUnKnownfalsetrue