CONSOLIDATED STATEMENTS OF CASH FLOWS $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 25, 2016 USD ($)	Dec. 27, 2015 USD ($)
Operating activities:
Net income (loss)	$ (42.7)	$ (60.5)	$ 19.8
Income (loss) from discontinued operations	(0.1)	(0.1)	53.0
Loss from continuing operations	(42.6)	(60.4)	(33.2)
Adjustments to reconcile loss from continuing operations to net cash used in operating activities from continuing operations:
Depreciation and amortization	22.5	22.8	25.5
Deferred income taxes	(10.2)	4.7	0.9
Stock-based compensation	7.8	5.1	6.1
Goodwill impairment charge	24.2	0.0	0.0
Loss (gain) on extinguishment of debt	17.3	(0.2)	3.4
Non-cash income tax benefit	0.0	0.0	(18.7)
Amortization of deferred financing costs	1.3	1.5	1.9
Amortization of premium and discount on Senior Secured Notes	0.7	0.9	1.1
Provision for doubtful accounts	0.1	0.3	0.4
Litigation related charges	0.0	1.7	0.0
Provision for non-cash restructuring charges	0.0	9.1	0.0
Change in accrual for excess facilities	0.0	0.0	(2.3)
Changes in assets and liabilities, net of acquisitions:
Accounts receivable	(39.1)	(24.7)	10.3
Inventoried costs	7.1	(2.7)	(8.2)
Prepaid expenses	(4.0)	1.8	(3.5)
Other assets	(2.6)	3.2	(3.2)
Accounts payable	(3.4)	2.9	2.9
Accrued expenses	(5.4)	16.5	0.6
Accrued compensation	(4.4)	2.3	(4.4)
Accrued interest	(1.9)	(0.3)	1.5
Billings in excess of costs and earnings on uncompleted contracts	5.4	(0.4)	(7.3)
Income tax receivable and payable	1.7	1.2	(3.1)
Other liabilities	(1.5)	2.3	(0.4)
Net cash used in operating activities from continuing operations	(27.0)	(12.4)	(29.7)
Investing activities:
Cash paid for acquisitions, net of cash acquired	0.0	(5.1)	0.0
Proceeds from sale of assets	0.7	0.1	0.9
Change in restricted cash	0.0	0.3	4.7
Capital expenditures	(26.5)	(9.2)	(11.3)
Net cash used in investing activities from continuing operations	(25.8)	(13.9)	(5.7)
Financing activities:
Proceeds from the issuance of long-term debt	300.0	0.0	0.0
Extinguishment of long-term debt	(448.8)	(14.1)	(175.0)
Proceeds from the issuance of common stock	269.1	76.2	0.0
Repayments under credit facility	(1.0)	(1.0)	(42.0)
Cash paid for contingent acquisition consideration	0.0	0.0	(1.1)
Debt issuance costs	(6.6)	0.0	0.0
Proceeds from exercise of restricted stock units, employee stock options, and employee stock purchase plan	1.5	2.0	3.4
Other	(0.8)	0.0	0.0
Net cash provided by (used in) financing activities from continuing operations	113.4	63.1	(214.7)
Net cash flows of continuing operations	60.6	36.8	(250.1)
Net operating cash flows of discontinued operations	0.0	0.1	2.8
Net investing cash flows of discontinued operations	(0.6)	4.0	242.5
Effect of exchange rate changes on cash and cash equivalents	0.5	(0.3)	(0.2)
Net increase (decrease) in cash and cash equivalents	60.5	40.6	(5.0)
Cash and cash equivalents at beginning of year	69.1	28.5	33.5
Cash and cash equivalents at end of year	129.6	69.1	28.5
Supplemental disclosure of cash flow information:
Cash paid during the year for interest	28.3	32.4	43.8
Net cash paid during the year for income taxes	(0.9)	0.0	8.8
Noncash Investing and Financing Items [Abstract]
Capital expenditures included in accounts payable and accrued expenses	1.6	2.1	0.0
Liability for contingent consideration and goodwill related to acquisition	$ 0.0	$ 5.1	$ 0.0