Segment Information (Details) $ in Millions	3 Months Ended
	Mar. 28, 2021 USD ($) segment	Mar. 29, 2020 USD ($)	Dec. 27, 2020 USD ($)
Segment Reporting [Abstract]
Number of operating segments | segment	2
Number of reportable segments | segment	2
Segment Information
Revenues	$ 423.5	$ 366.6
Operating expenses:
Selling, general and administrative	43.4	38.0
Depreciation and amortization	19.8	22.5
Total operating expenses	314.0	291.5
Operating profit	109.5	75.1
Interest expense, net	13.0	16.0
Other income, net	(0.4)	(0.7)
Intercompany (income) expense	0.0
Income before income taxes	96.9	59.8
Income taxes	24.4	15.1
Net income	72.5	44.7
Total assets	2,625.8	2,215.5	$ 2,528.9
Service revenues
Segment Information
Revenues	360.4	334.0
Operating expenses:
Cost of service and vehicle sales	196.4	203.2
Vehicle sales
Segment Information
Revenues	63.1	32.6
Operating expenses:
Cost of service and vehicle sales	54.4	27.8
United States
Segment Information
Revenues	358.3	321.1
Operating expenses:
Selling, general and administrative	40.5	35.1
Depreciation and amortization	17.9	20.8
Total operating expenses	257.5	253.9
Operating profit	100.8	67.2
Interest expense, net	13.0	16.1
Other income, net	(0.2)	(0.1)
Intercompany (income) expense	(2.3)
Income before income taxes	90.3	51.2
Income taxes	22.7	12.8
Net income	67.6	38.4
Total assets	2,392.9	2,036.4
United States | Service revenues
Segment Information
Revenues	332.4	305.0
Operating expenses:
Cost of service and vehicle sales	178.1	185.0
United States | Vehicle sales
Segment Information
Revenues	25.9	16.1
Operating expenses:
Cost of service and vehicle sales	21.0	13.0
International
Segment Information
Revenues	65.2	45.5
Operating expenses:
Selling, general and administrative	2.9	2.9
Depreciation and amortization	1.9	1.7
Total operating expenses	56.5	37.6
Operating profit	8.7	7.9
Interest expense, net	0.0	(0.1)
Other income, net	(0.2)	(0.6)
Intercompany (income) expense	2.3
Income before income taxes	6.6	8.6
Income taxes	1.7	2.3
Net income	4.9	6.3
Total assets	232.9	179.1
International | Service revenues
Segment Information
Revenues	28.0	29.0
Operating expenses:
Cost of service and vehicle sales	18.3	18.2
International | Vehicle sales
Segment Information
Revenues	37.2	16.5
Operating expenses:
Cost of service and vehicle sales	$ 33.4	$ 14.8