CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 26, 2021	Dec. 27, 2020	Dec. 29, 2019
Operating activities:
Net income (loss)	$ (1.6)	$ 79.4	$ 12.6
Income (loss) from discontinued operations	(2.1)	(0.9)	1.7
Income from continuing operations	0.5	80.3	10.9
Adjustments to reconcile income from continuing operations to net cash provided by operating activities from continuing operations:
Depreciation and amortization	25.7	24.6	23.4
Deferred income taxes	(0.4)	(78.2)	(4.9)
Amortization of lease right-of-use assets	9.0	9.4	11.7
Stock-based compensation	25.8	21.0	11.0
Amortization of deferred financing costs	1.0	1.0	1.0
Recovery of doubtful accounts	(0.2)	0.0	(0.2)
Changes in assets and liabilities, net of acquisitions:
Accounts receivable	2.6	(3.7)	(11.6)
Unbilled receivables	(15.7)	3.6	(1.6)
Inventoried costs	(5.3)	(5.3)	(4.6)
Prepaid expenses	2.4	(2.1)	0.3
Other assets	(6.9)	(8.7)	(0.9)
Operating lease liabilities	(9.3)	(10.2)	(6.3)
Accounts payable	(5.3)	(2.4)	4.8
Accrued expenses	(7.4)	1.0	(6.4)
Accrued compensation	(1.3)	8.5	1.7
Accrued interest	(0.1)	(0.1)	(0.1)
Billings in excess of costs and earnings on uncompleted contracts	24.1	(5.0)	(2.4)
Income tax receivable and payable	1.4	(1.1)	1.8
Other liabilities	(5.3)	12.1	1.3
Net cash provided by operating activities from continuing operations	35.3	44.7	28.9
Investing activities:
Cash paid for acquisitions, net of cash acquired	(12.3)	(51.5)	(17.7)
Proceeds from sale of assets	2.2	0.1	0.3
Proceeds from insurance	4.5	0.0	0.0
Capital expenditures	(46.5)	(35.9)	(26.3)
Net cash used in investing activities from continuing operations	(52.1)	(87.3)	(43.7)
Financing activities:
Proceeds from the issuance of long-term debt	0.0	5.1	0.0
Proceeds from the issuance of common stock	0.0	240.4	0.0
Repayment under credit facility and debt	(5.1)	(0.6)	0.0
Payments of employee taxes withheld from share-based awards	(9.1)	(1.4)	(0.9)
Payments under finance leases	(1.0)	(0.6)	(0.5)
Proceeds from shares issued under equity plans	5.9	4.8	4.9
Net cash provided (used in) by financing activities from continuing operations	(9.3)	247.7	3.5
Net cash flows of continuing operations	(26.1)	205.1	(11.3)
Net operating cash flows of discontinued operations	(4.5)	1.9	1.1
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(1.5)	1.9	(0.2)
Net increase (decrease) in cash, cash equivalents and restricted cash	(32.1)	208.9	(10.4)
Cash, cash equivalents and restricted cash at beginning of year	381.5	172.6	183.0
Cash, cash equivalents and restricted cash at end of year	349.4	381.5	172.6
Supplemental disclosure of cash flow information:
Cash paid during the year for interest	19.9	19.9	19.9
Net cash paid during the year for income taxes	2.0	2.5	0.6
Non-cash financing and investing activities:
Capital expenditures included in accounts payable and accrued expenses	$ 3.0	$ 2.9	$ 1.4