CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Oct. 01, 2023	Sep. 25, 2022	Oct. 01, 2023	Sep. 25, 2022	Dec. 25, 2022
Operating activities:
Net loss	$ 3.0	$ (8.0)	$ (3.2)	$ (28.3)
Income from discontinued operations	0.0	0.0	0.2	0.7
Income (loss) from continuing operations	3.0	(8.0)	(3.4)	(29.0)
Adjustments to reconcile loss from continuing operations to net cash used in operating activities from continuing operations:
Depreciation and amortization	8.2	8.9	24.0	22.8
Deferred income taxes			0.1	0.3
Amortization of lease right-of-use assets			8.5	7.8
Stock-based compensation			19.0	19.9
Amortization of deferred financing costs			0.5	0.6
Loss on extinguishment of debt	0.0	0.0	0.0	13.0
Provision for doubtful accounts			1.0	0.0
Litigation related charges			0.0	5.5
Changes in assets and liabilities, net of acquisitions:
Accounts receivable			(23.5)	17.0
Unbilled receivables			(9.1)	(18.2)
Inventoried costs			(23.7)	(28.0)
Prepaid expenses and other assets			(15.7)	(17.4)
Operating lease liabilities			(8.2)	(7.7)
Accounts payable			(0.6)	1.0
Accrued expenses			6.4	1.1
Accrued compensation			3.1	3.0
Accrued interest			0.3	(1.2)
Billings in excess of costs and earnings on uncompleted contracts			17.4	(10.6)
Income tax receivable and payable			1.9	(8.3)
Other liabilities			(0.2)	(3.9)
Net cash used in operating activities from continuing operations			(2.2)	(32.3)
Investing activities:
Cash paid for acquisitions, net of cash acquired			0.0	(132.2)
Proceeds from sale of assets			8.3	0.1
Capital expenditures			(33.1)	(34.8)
Net cash used in investing activities from continuing operations			(24.8)	(166.9)
Financing activities:
Proceeds from the issuance of long-term debt			0.0	200.0
Borrowing under credit facility			54.0	100.0
Redemption of Senior Secured Notes			0.0	(309.8)
Repayment under credit facility and term loan			(67.8)	(1.2)
Debt issuance costs			0.0	(3.2)
Payments under finance leases	(0.4)	(0.4)	(1.2)	(1.0)
Payments of employee taxes withheld from share-based awards			(3.6)	(12.3)
Proceeds from shares issued under equity plans			6.5	6.1
Net cash used in financing activities from continuing operations			(12.1)	(21.4)
Net cash used in continuing operations			(39.1)	(220.6)
Net operating cash flows of discontinued operations			0.0	(0.3)
Effect of exchange rate changes on cash, cash equivalents and restricted cash			0.0	(3.3)
Net decrease in cash, cash equivalents and restricted cash			(39.1)	(224.2)
Cash, cash equivalents and restricted cash at beginning of period			81.3	349.4	$ 349.4
Cash, cash equivalents and restricted cash at end of period	42.2	125.2	42.2	125.2	$ 81.3
Significant non-cash investing and financing activities:
Financing lease obligation incurred	$ 0.0	$ 0.0	0.1	9.1
Common stock issuance for purchase of noncontrolling interests			10.7	2.7
Common stock issuance for acquisition			$ 0.0	$ 5.0