Acquisitions - Net Assets Acquired (Details) (USD $)	3 Months Ended
	Apr. 27, 2013	Dec. 03, 2012	Jul. 28, 2012
BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract [Abstract]
Cash and equivalents		$ 200,000
Accounts receivable, net		113,200,000
Costs and estimated earnings in excess of billings		60,900,000
Inventories		9,000,000
Other current assets		1,700,000
Property and equipment		32,600,000
Goodwill	260,708,000	85,900,000	174,849,000
Carrying amount		91,100,000
Other assets		2,400,000
Total assets		397,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities [Abstract]
Accounts payable		41,400,000
Billings in excess of costs and estimated earnings		10,300,000
Accrued and other liabilities		26,200,000
Total liabilities		77,900,000
Net Assets Acquired		319,100,000
Goodwill purchase adjustment	2,300,000
Asset fair value adjustment	2,500,000
Working capital adjustment	200,000
Customer Relationships
BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract [Abstract]
Carrying amount	160,645,000		89,145,000
Intangibles		71,500,000
Backlog
BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract [Abstract]
Intangibles		14,400,000
Trade Names
BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract [Abstract]
Carrying amount	8,025,000		2,860,000
Intangibles		$ 5,200,000