2.2.0.25falsefalse21100 - Disclosure - Retirement Plans (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_RetirementPlansPoliciesAbstractwatfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringNo definition available.falsefalseRetirement Plans (Policies) [Abstract]3false0wat_PensionAndOtherPostretirementPlansPolicyTextBlockwatfalsenadurationDescribes an entity's accounting policy for its pension and other postretirement benefit plans. This disclosure may address...falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00<p style='margin-top:0pt; margin-bottom:0pt'><font style="font-family:Times New Roman;font-size:10pt;margin-left:0px;">The net periodic pension cost is made up of several components that reflect different aspects of the Company's financial arrangements as well as the cost of benefits earned by employees. These components are determined using the projected unit credit actuarial cost method and are based on certain actuarial assumptions. The Company's accounting policy is to reflect in the projected benefit obligation all benefit changes to which the Company is committed as of the current valuation date; use a market-related value of assets to determine pension expense; amortize increases in prior service costs on a straight-line basis over the expected future service of active participants as of the date such costs are first recognized; and amortize cumulative actuarial gains and losses in excess of 10% of the larger of the market-related value of plan assets and the projected benefit obligation over the expected future service of active participants.</font></p>The net periodic pension cost is made up of several components that reflect different aspects of the Company's financial arrangements as well as the cost offalsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDescribes an entity's accounting policy for its pension and other postretirement benefit plans. This disclosure may address (1) the types of plans sponsored by the entity, and the benefits provided by each plan (2) groups that participate in (or are covered by) each plan (3) how plan assets, liabilities and expenses are measured, including the use of any actuaries and (4) significant assumptions used by the entity to value plan assets and liabilities and how such assumptions are derived.No authoritative reference available.falsefalsePension and Other Postretirement Plans Policy12Retirement Plans (Policies)UnKnownUnKnownUnKnownUnKnownfalsetrue