Assets and liabilities measured at fair value (Details) (USD $) In Thousands	Jul. 29, 2011
Fair value measurements on recurring basis | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1)
Assets:
Trading securities	$ 7,170
Liabilities:
Long-term obligations	2,818,714
Deferred compensation	18,700
Fair value measurements on recurring basis | Significant Other Observable Inputs (Level 2)
Liabilities:
Long-term obligations	20,174
Derivative financial instruments	20,092
Fair value measurements on recurring basis | Balance at the end of the period
Assets:
Trading securities	7,170
Liabilities:
Long-term obligations	2,838,888
Derivative financial instruments	20,092
Deferred compensation	18,700
Reported amount | Prepaid expenses and other current assets
Assets:
Trading securities	1,738
Reported amount | Other assets, net
Assets:
Trading securities	5,432
Reported amount | Current portion of long-term debt obligations
Liabilities:
Long-term obligations	963
Reported amount | Long-term obligations
Liabilities:
Long-term obligations	2,779,408
Reported amount | Accrued expenses and other current liabilities
Liabilities:
Derivative financial instruments	11,156
Deferred compensation	1,738
Reported amount | Non-current Other Liabilities
Liabilities:
Derivative financial instruments	8,936
Deferred compensation	$ 16,962