1.0.0.3 false Consolidated Balance Sheets (USD $) In Thousands false 1 $ false false Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDEPS Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 false 2 $ false false Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDEPS Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 6 Current assets: 4 us-gaap_AssetsCurrentAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 7 Cash and cash equivalents 5 us-gaap_CashAndCashEquivalentsAtCarryingValue us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 true true 341111000 341111 false false 2 true true 428522000 428522 false false No definition available. No authoritative reference available. false 8 Short-term investments 5 us-gaap_ShortTermInvestments us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 289146000 289146 false false 2 false true 0 0 false false No definition available. No authoritative reference available. false 9 Accounts receivable, less allowances for doubtful accounts and sales returns of $6,723 and $7,608 at December 31, 2009 and December 31, 2008, respectively 5 us-gaap_AccountsReceivableNetCurrent us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 314247000 314247 false false 2 false true 291763000 291763 false false No definition available. No authoritative reference available. false 10 Inventories 5 us-gaap_InventoryNet us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 178666000 178666 false false 2 false true 173051000 173051 false false No definition available. No authoritative reference available. false 11 Other current assets 5 us-gaap_OtherAssetsCurrent us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 49206000 49206 false false 2 false true 62966000 62966 false false No definition available. No authoritative reference available. true 12 Total current assets 5 us-gaap_AssetsCurrent us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 1172376000 1172376 false false 2 false true 956302000 956302 false false No definition available. No authoritative reference available. false 13 Property, plant and equipment, net 4 us-gaap_PropertyPlantAndEquipmentNet us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 210926000 210926 false false 2 false true 171588000 171588 false false No definition available. No authoritative reference available. false 14 Intangible assets, net 4 us-gaap_IntangibleAssetsNetExcludingGoodwill us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 182165000 182165 false false 2 false true 149652000 149652 false false No definition available. No authoritative reference available. false 15 Goodwill 4 us-gaap_Goodwill us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 293077000 293077 false false 2 false true 268364000 268364 false false No definition available. No authoritative reference available. false 16 Other assets 4 us-gaap_OtherAssetsNoncurrent us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 49387000 49387 false false 2 false true 76992000 76992 false false No definition available. No authoritative reference available. true 17 Total assets 4 us-gaap_Assets us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 1907931000 1907931 false false 2 false true 1622898000 1622898 false false No definition available. No authoritative reference available. true 20 Current liabilities: 5 us-gaap_LiabilitiesCurrentAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 21 Notes payable and debt 6 us-gaap_DebtCurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 131772000 131772 false false 2 false true 36120000 36120 false false No definition available. No authoritative reference available. false 22 Accounts payable 6 us-gaap_AccountsPayableCurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 49573000 49573 false false 2 false true 47240000 47240 false false No definition available. No authoritative reference available. false 23 Accrued employee compensation 6 us-gaap_EmployeeRelatedLiabilitiesCurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 37050000 37050 false false 2 false true 43535000 43535 false false No definition available. No authoritative reference available. false 24 Deferred revenue and customer advances 6 wat_DeferredRevenueAndCustomerAdvances wat false credit instant monetary Deferred revenue and customer advances false false false false false false false false false 1 false true 94680000 94680 false false 2 false true 87492000 87492 false false Deferred revenue and customer advances No authoritative reference available. false 25 Accrued income taxes 6 us-gaap_AccruedIncomeTaxesCurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 13267000 13267 false false 2 false true 0 0 false false No definition available. No authoritative reference available. false 26 Accrued warranty 6 wat_AccruedWarranty wat false credit instant monetary Accrued warranty false false false false false false false false false 1 false true 10109000 10109 false false 2 false true 10276000 10276 false false Accrued warranty No authoritative reference available. false 27 Other current liabilities 6 us-gaap_OtherLiabilitiesCurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 58117000 58117 false false 2 false true 64843000 64843 false false No definition available. No authoritative reference available. true 28 Total current liabilities 6 us-gaap_LiabilitiesCurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 394568000 394568 false false 2 false true 289506000 289506 false false No definition available. No authoritative reference available. false 29 Long-term liabilities: 5 us-gaap_LiabilitiesNoncurrentAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 30 Long-term debt 6 us-gaap_LongTermDebtNoncurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 500000000 500000 false false 2 false true 500000000 500000 false false No definition available. No authoritative reference available. false 31 Long-term portion of retirement benefits 6 us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 69044000 69044 false false 2 false true 77017000 77017 false false No definition available. No authoritative reference available. false 32 Long-term income tax liability 6 us-gaap_AccruedIncomeTaxesNoncurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 72604000 72604 false false 2 false true 80310000 80310 false false No definition available. No authoritative reference available. false 33 Other long-term liabilities 6 us-gaap_OtherLiabilitiesNoncurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 22766000 22766 false false 2 false true 15060000 15060 false false No definition available. No authoritative reference available. true 34 Total long-term liabilities 6 us-gaap_LiabilitiesNoncurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 664414000 664414 false false 2 false true 672387000 672387 false false No definition available. No authoritative reference available. true 35 Total liabilities 5 us-gaap_Liabilities us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 1058982000 1058982 false false 2 false true 961893000 961893 false false No definition available. No authoritative reference available. false 38 Stockholders' equity: 5 us-gaap_StockholdersEquityAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 39 Preferred stock, par value $0.01 per share, 5,000 shares authorized, none issued at December 31, 2009 and December 31, 2008 6 us-gaap_PreferredStockValue us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 0 0 false false 2 false true 0 0 false false No definition available. No authoritative reference available. false 40 Common stock, par value $0.01 per share, 400,000 shares authorized, 148,831 and 148,069 shares issued, 94,118 and 97,891 shares outstanding at December 31, 2009 and December 31, 2008, respectively 6 us-gaap_CommonStockValue us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 1488000 1488 false false 2 false true 1481000 1481 false false No definition available. No authoritative reference available. false 41 Additional paid-in capital 6 us-gaap_AdditionalPaidInCapital us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 808345000 808345 false false 2 false true 756499000 756499 false false No definition available. No authoritative reference available. false 42 Retained earnings 6 us-gaap_RetainedEarningsAccumulatedDeficit us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 2236716000 2236716 false false 2 false true 1913403000 1913403 false false No definition available. No authoritative reference available. false 43 Treasury stock, at cost, 54,713 and 50,178 shares at December 31, 2009 and December 31, 2008, respectively 6 us-gaap_TreasuryStockValue us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true -2213174000 -2213174 false false 2 false true -2001797000 -2001797 false false No definition available. No authoritative reference available. false 44 Accumulated other comprehensive income (loss) 6 us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 15574000 15574 false false 2 false true -8581000 -8581 false false No definition available. No authoritative reference available. true 45 Total stockholders' equity 6 us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 848949000 848949 false false 2 false true 661005000 661005 false false No definition available. No authoritative reference available. true 46 Total liabilities and stockholders' equity 4 us-gaap_LiabilitiesAndStockholdersEquity us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 true true 1907931000 1907931 false false 2 true true 1622898000 1622898 false false No definition available. No authoritative reference available. true false 2 37 false Thousands UnKnown UnKnown false true