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Summary of Significant Accounting Policies - Reconciliation of Basic and Diluted Net Income Per Share (Detail) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
 3 Months Ended
Mar. 31, 2018
Apr. 01, 2017
Accounting Policies [Abstract]    
Options to purchase of shares of common stock 900 100
Net income attributable to stockholders of Masimo Corporation:    
Net income $ 45,630 $ 51,533
Net income 45,630 51,533
Net income    
Net income $ 45,630 $ 51,533
Weighted-average shares outstanding - basic 51,709 50,652
Net income per basic share $ 0.88 $ 1.02
Diluted net income per share:    
Weighted-average shares outstanding - basic 51,709 50,652
Diluted share equivalent: stock options and RSUs 3,787 4,877
Weighted-average shares outstanding - diluted 55,496 55,529
Net income per diluted share $ 0.82 $ 0.93