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Basis of Presentation and Summary of Significant Accounting Policies - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($)
$ in Thousands
Mar. 31, 2018
Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Available for sale securities $ 2,026,281 $ 2,945,758
US Treasury Securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Available for sale securities 425,032 591,988
Foreign Government Securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Available for sale securities 6,947 6,952
Corporate Debt Securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Available for sale securities 1,292,878 1,975,160
Time Deposits [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Available for sale securities 301,277 371,511
Equity Securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Available for sale securities 147 147
Fair Value, Measurements, Recurring [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Waters 401(k) Restoration Plan assets 35,762 35,645
Foreign currency exchange contracts 129 566
Total 2,062,172 2,981,969
Contingent consideration 3,399 3,247
Foreign currency exchange contracts 730 182
Total 4,129 3,429
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Waters 401(k) Restoration Plan assets 35,762 35,645
Total 35,762 35,645
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 2) [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Foreign currency exchange contracts 129 566
Total 2,026,410 2,946,324
Foreign currency exchange contracts 730 182
Total 730 182
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Contingent consideration 3,399 3,247
Total 3,399 3,247
Fair Value, Measurements, Recurring [Member] | US Treasury Securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Available for sale securities 425,032 591,988
Fair Value, Measurements, Recurring [Member] | US Treasury Securities [Member] | Significant Unobservable Inputs (Level 2) [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Available for sale securities 425,032 591,988
Fair Value, Measurements, Recurring [Member] | Foreign Government Securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Available for sale securities 6,947 6,952
Fair Value, Measurements, Recurring [Member] | Foreign Government Securities [Member] | Significant Unobservable Inputs (Level 2) [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Available for sale securities 6,947 6,952
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Available for sale securities 1,292,878 1,975,160
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Significant Unobservable Inputs (Level 2) [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Available for sale securities 1,292,878 1,975,160
Fair Value, Measurements, Recurring [Member] | Time Deposits [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Available for sale securities 301,277 371,511
Fair Value, Measurements, Recurring [Member] | Time Deposits [Member] | Significant Unobservable Inputs (Level 2) [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Available for sale securities 301,277 371,511
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Available for sale securities 147 147
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Significant Unobservable Inputs (Level 2) [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Available for sale securities $ 147 $ 147