Condensed Consolidating Financial Statements - Balance Sheet (Details) - USD ($)	Sep. 27, 2015	Dec. 28, 2014	Sep. 28, 2014	May. 31, 2014	Dec. 29, 2013
Condensed Financial Statements, Captions [Line Items]
Principal	$ 453,000,000	$ 669,800,000
Current assets:
Cash and cash equivalents	35,800,000	33,500,000	$ 16,100,000		$ 54,200,000
Accounts receivable, net	194,700,000	217,500,000
Amounts due from affiliated companies	0	0
Inventoried costs	54,600,000	47,400,000
Other current assets	25,300,000	22,700,000
Current assets of discontinued operations	0	53,800,000
Total current assets	310,400,000	374,900,000
Property, plant and equipment, net	60,700,000	61,600,000
Goodwill	483,400,000	483,400,000
Intangible assets, net	39,400,000	49,500,000
Investment in subsidiaries	0	0
Other assets	27,600,000	32,400,000
Non-current assets of discontinued operations	0	137,000,000
Total assets	921,500,000	1,138,800,000
Current liabilities:
Accounts payable	28,100,000	44,600,000
Accrued expenses	38,400,000	38,000,000
Accrued compensation	30,000,000	41,100,000
Billings in excess of costs and earnings on uncompleted contracts	49,200,000	49,600,000
Deferred income tax liability	30,200,000	30,300,000
Amounts due to affiliated companies	0	0
Other current liabilities	9,900,000	7,900,000
Current liabilities of discontinued operations	1,500,000	14,600,000
Total current liabilities	187,300,000	226,100,000
Long-term debt, net of current portion	448,500,000	663,000,000
Other long-term liabilities	23,900,000	24,900,000
Non-current liabilities of discontinued operations	4,200,000	500,000
Total liabilities	663,900,000	914,500,000
Total stockholders' equity	257,600,000	224,300,000
Total liabilities and stockholders’ equity	$ 921,500,000	1,138,800,000
Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Ownership percentage	100.00%
Parent Company
Current assets:
Cash and cash equivalents	$ 30,600,000	28,700,000
Accounts receivable, net	0	0
Amounts due from affiliated companies	201,100,000	341,900,000
Inventoried costs	0	0
Other current assets	8,000,000	4,400,000
Current assets of discontinued operations	0	0
Total current assets	239,700,000	375,000,000
Property, plant and equipment, net	1,800,000	2,000,000
Goodwill	0	0
Intangible assets, net	0	0
Investment in subsidiaries	476,300,000	498,300,000
Other assets	25,100,000	27,800,000
Non-current assets of discontinued operations	0	0
Total assets	742,900,000	903,100,000
Current liabilities:
Accounts payable	2,800,000	3,100,000
Accrued expenses	13,200,000	6,300,000
Accrued compensation	3,200,000	5,200,000
Billings in excess of costs and earnings on uncompleted contracts	0	0
Deferred income tax liability	0	0
Amounts due to affiliated companies	0	0
Other current liabilities	4,100,000	300,000
Current liabilities of discontinued operations	1,400,000	700,000
Total current liabilities	24,700,000	15,600,000
Long-term debt, net of current portion	446,500,000	660,200,000
Other long-term liabilities	9,900,000	3,000,000
Non-current liabilities of discontinued operations	4,200,000	0
Total liabilities	485,300,000	678,800,000
Total stockholders' equity	257,600,000	224,300,000
Total liabilities and stockholders’ equity	742,900,000	903,100,000
Subsidiary Guarantors on a Combined Basis
Current assets:
Cash and cash equivalents	(4,900,000)	(5,500,000)
Accounts receivable, net	174,100,000	196,400,000
Amounts due from affiliated companies	0	0
Inventoried costs	34,300,000	32,200,000
Other current assets	13,000,000	15,500,000
Current assets of discontinued operations	0	38,700,000
Total current assets	216,500,000	277,300,000
Property, plant and equipment, net	52,000,000	52,000,000
Goodwill	442,600,000	442,600,000
Intangible assets, net	39,400,000	49,400,000
Investment in subsidiaries	56,600,000	48,100,000
Other assets	2,400,000	4,600,000
Non-current assets of discontinued operations	0	134,500,000
Total assets	809,500,000	1,008,500,000
Current liabilities:
Accounts payable	21,100,000	37,100,000
Accrued expenses	22,000,000	28,900,000
Accrued compensation	23,700,000	32,700,000
Billings in excess of costs and earnings on uncompleted contracts	45,700,000	45,700,000
Deferred income tax liability	30,200,000	30,300,000
Amounts due to affiliated companies	161,600,000	287,400,000
Other current liabilities	5,000,000	6,100,000
Current liabilities of discontinued operations	0	10,800,000
Total current liabilities	309,300,000	479,000,000
Long-term debt, net of current portion	0	0
Other long-term liabilities	11,900,000	19,000,000
Non-current liabilities of discontinued operations	0	200,000
Total liabilities	321,200,000	498,200,000
Total stockholders' equity	488,300,000	510,300,000
Total liabilities and stockholders’ equity	809,500,000	1,008,500,000
Non-Guarantors on a Combined Basis
Current assets:
Cash and cash equivalents	10,100,000	10,300,000
Accounts receivable, net	20,600,000	21,100,000
Amounts due from affiliated companies	0	0
Inventoried costs	20,300,000	15,200,000
Other current assets	4,300,000	2,800,000
Current assets of discontinued operations	0	15,100,000
Total current assets	55,300,000	64,500,000
Property, plant and equipment, net	6,900,000	7,600,000
Goodwill	40,800,000	40,800,000
Intangible assets, net	0	100,000
Investment in subsidiaries	0	0
Other assets	100,000	0
Non-current assets of discontinued operations	0	2,500,000
Total assets	103,100,000	115,500,000
Current liabilities:
Accounts payable	4,200,000	4,400,000
Accrued expenses	3,200,000	2,800,000
Accrued compensation	3,100,000	3,200,000
Billings in excess of costs and earnings on uncompleted contracts	3,500,000	3,900,000
Deferred income tax liability	0	0
Amounts due to affiliated companies	39,500,000	54,500,000
Other current liabilities	800,000	1,500,000
Current liabilities of discontinued operations	100,000	3,100,000
Total current liabilities	54,400,000	73,400,000
Long-term debt, net of current portion	2,000,000	2,800,000
Other long-term liabilities	2,100,000	2,900,000
Non-current liabilities of discontinued operations	0	300,000
Total liabilities	58,500,000	79,400,000
Total stockholders' equity	44,600,000	36,100,000
Total liabilities and stockholders’ equity	103,100,000	115,500,000
Eliminations
Current assets:
Cash and cash equivalents	0	0
Accounts receivable, net	0	0
Amounts due from affiliated companies	(201,100,000)	(341,900,000)
Inventoried costs	0	0
Other current assets	0	0
Current assets of discontinued operations	0	0
Total current assets	(201,100,000)	(341,900,000)
Property, plant and equipment, net	0	0
Goodwill	0	0
Intangible assets, net	0	0
Investment in subsidiaries	(532,900,000)	(546,400,000)
Other assets	0	0
Non-current assets of discontinued operations	0	0
Total assets	(734,000,000)	(888,300,000)
Current liabilities:
Accounts payable	0	0
Accrued expenses	0	0
Accrued compensation	0	0
Billings in excess of costs and earnings on uncompleted contracts	0	0
Deferred income tax liability	0	0
Amounts due to affiliated companies	(201,100,000)	(341,900,000)
Other current liabilities	0	0
Current liabilities of discontinued operations	0	0
Total current liabilities	(201,100,000)	(341,900,000)
Long-term debt, net of current portion	0	0
Other long-term liabilities	0	0
Non-current liabilities of discontinued operations	0	0
Total liabilities	(201,100,000)	(341,900,000)
Total stockholders' equity	(532,900,000)	(546,400,000)
Total liabilities and stockholders’ equity	(734,000,000)	$ (888,300,000)
Senior notes | 7% Senior Notes due 2019
Condensed Financial Statements, Captions [Line Items]
Principal	$ 450,000,000			$ 625,000,000.0