Condensed Consolidating Financial Statements - Condensed Consolidating Balance Sheet (Details) - USD ($)	Dec. 25, 2016	Dec. 27, 2015	Dec. 28, 2014	May 31, 2014	Dec. 29, 2013
Condensed Financial Statements, Captions [Line Items]
Principal	$ 437,300,000.0	$ 452,700,000.0
Ownership percentage	100.00%
Current assets:
Cash and cash equivalents	$ 69,100,000	28,500,000	$ 33,500,000		$ 54,200,000
Accounts receivable, net	229,400,000	206,800,000
Amounts due from affiliated companies	0	0
Inventoried costs	55,400,000	55,600,000
Other current assets	19,200,000	29,500,000
Total current assets	373,100,000	320,400,000
Property, plant and equipment, net	49,800,000	56,200,000
Goodwill	485,400,000	483,400,000
Intangible assets, net	32,600,000	36,500,000
Investment in subsidiaries	0	0
Other assets	7,700,000	6,800,000
Total assets	948,600,000	903,300,000	1,131,200,000
Current liabilities:
Accounts payable	52,700,000	48,300,000
Accrued expenses	53,600,000	37,000,000
Accrued compensation	39,100,000	36,800,000
Billings in excess of costs and earnings on uncompleted contracts	41,800,000	42,300,000
Amounts due to affiliated companies	0	0
Other current liabilities	7,700,000	6,100,000
Current liabilities of discontinued operations	1,600,000	1,900,000
Total current liabilities	196,500,000	172,400,000
Long-term debt, net of current portion	431,000,000	444,100,000
Other long-term liabilities	41,000,000	28,500,000
Non-current liabilities of discontinued operations	3,700,000	4,100,000
Total liabilities	672,200,000	649,100,000
Total stockholders’ equity	276,400,000	254,200,000	$ 224,300,000		$ 295,800,000
Total liabilities and stockholders’ equity	948,600,000	903,300,000
Eliminations
Current assets:
Cash and cash equivalents	0	0
Accounts receivable, net	0	0
Amounts due from affiliated companies	(204,600,000)	(207,800,000)
Inventoried costs	0	0
Other current assets	0	0
Total current assets	(204,600,000)	(207,800,000)
Property, plant and equipment, net	0	0
Goodwill	0	0
Intangible assets, net	0	0
Investment in subsidiaries	(525,500,000)	(538,100,000)
Other assets	0	0
Total assets	(730,100,000)	(745,900,000)
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
Amounts due to affiliated companies	(204,600,000)	(207,800,000)
Other current liabilities	0	0
Current liabilities of discontinued operations	0	0
Total current liabilities	(204,600,000)	(207,800,000)
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	(204,600,000)	(207,800,000)
Total stockholders’ equity	(525,500,000)	(538,100,000)
Total liabilities and stockholders’ equity	(730,100,000)	(745,900,000)
Parent Company
Current assets:
Cash and cash equivalents	67,200,000	22,500,000
Accounts receivable, net	0	0
Amounts due from affiliated companies	204,600,000	207,800,000
Inventoried costs	0	0
Other current assets	6,300,000	16,400,000
Total current assets	278,100,000	246,700,000
Property, plant and equipment, net	1,600,000	2,000,000
Goodwill	0	0
Intangible assets, net	0	0
Investment in subsidiaries	458,000,000	477,800,000
Other assets	400,000	700,000
Total assets	738,100,000	727,200,000
Current liabilities:
Accounts payable	4,500,000	4,300,000
Accrued expenses	5,600,000	4,700,000
Accrued compensation	4,000,000	4,100,000
Billings in excess of costs and earnings on uncompleted contracts	0	0
Amounts due to affiliated companies	0	0
Other current liabilities	1,400,000	4,300,000
Current liabilities of discontinued operations	1,500,000	1,800,000
Total current liabilities	17,000,000	19,200,000
Long-term debt, net of current portion	430,200,000	442,400,000
Other long-term liabilities	10,800,000	7,300,000
Non-current liabilities of discontinued operations	3,700,000	4,100,000
Total liabilities	461,700,000	473,000,000
Total stockholders’ equity	276,400,000	254,200,000
Total liabilities and stockholders’ equity	738,100,000	727,200,000
Subsidiary Guarantors on a Combined Basis
Current assets:
Cash and cash equivalents	(3,300,000)	(4,800,000)
Accounts receivable, net	197,900,000	179,000,000
Amounts due from affiliated companies	0	0
Inventoried costs	37,200,000	36,900,000
Other current assets	11,600,000	11,700,000
Total current assets	243,400,000	222,800,000
Property, plant and equipment, net	41,700,000	47,500,000
Goodwill	442,500,000	442,600,000
Intangible assets, net	24,500,000	36,500,000
Investment in subsidiaries	67,500,000	60,300,000
Other assets	7,300,000	6,100,000
Total assets	826,900,000	815,800,000
Current liabilities:
Accounts payable	43,700,000	36,500,000
Accrued expenses	44,500,000	29,300,000
Accrued compensation	31,200,000	29,200,000
Billings in excess of costs and earnings on uncompleted contracts	38,900,000	37,100,000
Amounts due to affiliated companies	174,600,000	175,700,000
Other current liabilities	4,100,000	200,000
Current liabilities of discontinued operations	0	0
Total current liabilities	337,000,000	308,000,000
Long-term debt, net of current portion	0	0
Other long-term liabilities	19,900,000	18,000,000
Non-current liabilities of discontinued operations	0	0
Total liabilities	356,900,000	326,000,000
Total stockholders’ equity	470,000,000	489,800,000
Total liabilities and stockholders’ equity	826,900,000	815,800,000
Non-Guarantors on a Combined Basis
Current assets:
Cash and cash equivalents	5,200,000	10,800,000
Accounts receivable, net	31,500,000	27,800,000
Amounts due from affiliated companies	0	0
Inventoried costs	18,200,000	18,700,000
Other current assets	1,300,000	1,400,000
Total current assets	56,200,000	58,700,000
Property, plant and equipment, net	6,500,000	6,700,000
Goodwill	42,900,000	40,800,000
Intangible assets, net	8,100,000	0
Investment in subsidiaries	0	0
Other assets	0	0
Total assets	113,700,000	106,200,000
Current liabilities:
Accounts payable	4,500,000	7,500,000
Accrued expenses	3,500,000	3,000,000
Accrued compensation	3,900,000	3,500,000
Billings in excess of costs and earnings on uncompleted contracts	2,900,000	5,200,000
Amounts due to affiliated companies	30,000,000	32,100,000
Other current liabilities	2,200,000	1,600,000
Current liabilities of discontinued operations	100,000	100,000
Total current liabilities	47,100,000	53,000,000
Long-term debt, net of current portion	800,000	1,700,000
Other long-term liabilities	10,300,000	3,200,000
Non-current liabilities of discontinued operations	0	0
Total liabilities	58,200,000	57,900,000
Total stockholders’ equity	55,500,000	48,300,000
Total liabilities and stockholders’ equity	113,700,000	$ 106,200,000
Senior notes | 7% Senior Notes due 2019
Condensed Financial Statements, Captions [Line Items]
Principal	$ 435,500,000			$ 625,000,000.0