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Postretirement Health Care Plans - Net Periodic Postretirement Health Care Cost (Detail) - Other Postretirement Benefit Plans, Defined Benefit [Member] - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2017
Oct. 01, 2016
Sep. 30, 2017
Oct. 01, 2016
Postretirement Health Care Plans [Line Items]        
Interest cost $ 0.5 $ 0.6 $ 1.5 $ 1.7
Expected return on plan assets (0.2) (0.3) (0.6) (0.7)
Amortization of unrecognized gain (0.1)   (0.2)  
Net periodic pension cost $ 0.2 $ 0.3 $ 0.7 $ 1.0