Fair value measurement Summary of the Non-Financial Assets Measured at Fair Value on Nonrecurring Basis (Details) (Fair Value, Measurements, Nonrecurring, USD $)	Dec. 30, 2012
Estimate of Fair Value, Fair Value Disclosure
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets held for sale	$ 17,508,000
Goodwill	29,610,000
Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets held for sale	0
Goodwill	0
Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets held for sale	0
Goodwill	0
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets held for sale	17,508,000
Goodwill	$ 29,610,000