Reportable Segments - Summary of Segment Data (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 26, 2020	Jun. 28, 2019	Jun. 26, 2020	Jun. 28, 2019	Dec. 27, 2019
Revenues:
Total segment revenues	$ 344.8	$ 265.4	$ 665.7	$ 525.5
Gross profit:
Total segment gross profit	73.9	48.2	139.6	93.0
Operating profit:
Total segment operating profit	30.8	9.0	53.4	17.2
ASSETS
Total segment assets	1,114.8		1,114.8		$ 1,019.3
SPS [Member]
Revenues:
Total segment revenues	277.9	210.4	537.3	410.6
Gross profit:
Total segment gross profit	48.6	29.3	93.3	55.0
Operating profit:
Total segment operating profit	24.3	6.4	44.6	10.7
ASSETS
Total segment assets	899.7		899.7		828.0
SSB [Member]
Revenues:
Total segment revenues	66.9	55.0	128.4	114.9
Gross profit:
Total segment gross profit	25.3	18.9	46.3	38.0
Operating profit:
Total segment operating profit	6.5	$ 2.6	8.8	$ 6.5
ASSETS
Total segment assets	$ 215.1		$ 215.1		$ 191.3