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	Jun. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	$ 1,677,723	$ 2,945,758
Waters 401(k) Restoration Plan assets	36,309	35,645
Foreign currency exchange contracts	167	566
Total	1,714,199	2,981,969
Contingent consideration	3,550	3,247
Foreign currency exchange contracts	875	182
Total	4,425	3,429
US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	237,759	591,988
Foreign Government Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	2,954	6,952
Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	1,198,549	1,975,160
Time Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	238,314	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, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Waters 401(k) Restoration Plan assets	36,309	35,645
Total	36,309	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	167	566
Total	1,677,890	2,946,324
Foreign currency exchange contracts	875	182
Total	875	182
Fair Value, Measurements, Recurring [Member] \| Significant Unobservable Inputs (Level 2) [Member] \| US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	237,759	591,988
Fair Value, Measurements, Recurring [Member] \| Significant Unobservable Inputs (Level 2) [Member] \| Foreign Government Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	2,954	6,952
Fair Value, Measurements, Recurring [Member] \| Significant Unobservable Inputs (Level 2) [Member] \| Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	1,198,549	1,975,160
Fair Value, Measurements, Recurring [Member] \| Significant Unobservable Inputs (Level 2) [Member] \| Time Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	238,314	371,511
Fair Value, Measurements, Recurring [Member] \| Significant Unobservable Inputs (Level 2) [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] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	3,550	3,247
Total	$ 3,550	$ 3,247

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