Acquisitions - Net Assets Acquired (Details) (USD $)	Jan. 26, 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		61,400,000
Inventories		9,000,000
Other current assets		1,700,000
Property and equipment		31,900,000
Goodwill	262,989,000	88,100,000	174,849,000
Carrying amount		91,100,000
Other assets		600,000
Total assets		397,200,000
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		25,800,000
Total liabilities		77,500,000
Net Assets Acquired		319,700,000
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