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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 9 Months Ended
Sep. 29, 2018
Sep. 30, 2017
Sep. 29, 2018
Sep. 30, 2017
Accounting Policies [Abstract]        
Options to purchase of shares of common stock 600 600 1,100 200
Net income attributable to stockholders of Masimo Corporation:        
Net income $ 57,126 $ 35,853 $ 146,609 $ 132,524
Net income 57,126 35,853 146,609 132,524
Net income        
Net income $ 57,126 $ 35,853 $ 146,609 $ 132,524
Weighted-average shares outstanding - basic 52,432 52,079 52,726 51,469
Net income per basic share $ 1.09 $ 0.69 $ 2.78 $ 2.57
Diluted net income per share:        
Weighted-average shares outstanding - basic 52,432 52,079 52,726 51,469
Diluted share equivalent: stock options and RSUs 3,805 4,084 3,829 4,498
Weighted-average shares outstanding - diluted 56,237 56,163 56,555 55,967
Net income per diluted share $ 1.02 $ 0.64 $ 2.59 $ 2.37