CONSOLIDATED STATEMENTS OF CASH FLOWS $ in Millions	12 Months Ended
	Dec. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 25, 2016 USD ($)
Operating activities:
Net loss	$ (3.5)	$ (42.7)	$ (60.5)
Income (loss) from discontinued operations	(7.6)	4.2	(2.9)
Income (loss) from continuing operations	4.1	(46.9)	(57.6)
Adjustments to reconcile income (loss) from continuing operations to net cash provided by (used in) operating activities from continuing operations:
Depreciation and amortization	17.9	22.2	22.5
Deferred income taxes	(0.4)	(9.5)	4.6
Stock-based compensation	7.2	7.8	5.1
Goodwill impairment charge	0.0	24.2	0.0
Loss (gain) on extinguishment of debt	0.0	17.3	(0.2)
Amortization of deferred financing costs	1.0	1.3	1.5
Amortization of premium and discount on Senior Secured Notes	0.0	0.7	0.9
Provision for doubtful accounts	1.8	0.0	0.1
Provision for non-cash restructuring charges	0.0	0.0	9.1
Changes in assets and liabilities, net of acquisitions:
Accounts receivable	8.2	0.5	(9.9)
Unbilled receivables	(35.9)	(35.2)	(17.9)
Inventoried costs	2.0	7.2	(2.5)
Prepaid expenses	2.2	(3.0)	1.7
Other assets	1.2	(2.7)	2.8
Accounts payable	12.2	(8.3)	1.7
Accrued expenses	(1.7)	(3.8)	20.6
Accrued compensation	3.3	(2.9)	2.5
Accrued interest	(0.1)	(1.9)	(0.3)
Billings in excess of costs and earnings on uncompleted contracts	(6.9)	6.3	(0.6)
Income tax receivable and payable	0.2	1.4	1.2
Other liabilities	1.8	(1.6)	0.1
Net cash provided by (used in) operating activities from continuing operations	18.1	(26.9)	(14.6)
Investing activities:
Cash paid for acquisitions, net of cash acquired	(2.9)	0.0	(5.1)
Proceeds from sale of assets	66.0	0.7	0.0
Capital expenditures	(22.6)	(26.1)	(9.0)
Net cash provided by (used in) investing activities from continuing operations	40.5	(25.4)	(14.1)
Financing activities:
Proceeds from the issuance of long-term debt	0.0	300.0	0.0
Extinguishment of long-term debt	0.0	(448.8)	(14.1)
Proceeds (expenses) from the issuance of common stock	(1.1)	269.1	76.2
Repayments under credit facility	(0.8)	(1.0)	(1.0)
Debt issuance costs	(0.1)	(6.6)	0.0
Proceeds from exercise of restricted stock units, employee stock options, and employee stock purchase plan	3.7	1.5	2.0
Other	0.0	(0.8)	0.0
Net cash provided by financing activities from continuing operations	1.7	113.4	63.1
Net cash flows of continuing operations	60.3	61.1	34.4
Net operating cash flows of discontinued operations	(7.7)	(0.8)	1.5
Net investing cash flows of discontinued operations	0.0	(0.6)	4.0
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(0.5)	0.5	(0.3)
Net increase in cash, cash equivalents and restricted cash	52.1	60.2	39.6
Cash, cash equivalents and restricted cash at beginning of year	130.9	70.7	31.1
Cash, cash equivalents and restricted cash at end of year	183.0	130.9	70.7
Supplemental disclosure of cash flow information:
Cash paid during the year for interest	20.5	28.3	32.4
Net cash paid during the year for income taxes	1.5	(0.6)	(0.1)
Noncash Investing and Financing Items [Abstract]
Capital expenditures included in accounts payable and accrued expenses	1.3	1.6	2.1
Liability for contingent consideration and goodwill related to acquisition	$ 0.0	$ 2.9	$ 5.1