Derivative financial instruments and fair value measurements (Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis ) (Details) - USD ($)		12 Months Ended
		Jan. 02, 2016		Jan. 03, 2015	Dec. 28, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Gain (Loss) on Derivatives		$ (143,000)		$ (176,000)	$ (1,976,000)
Contingent Consideration		(21,010,000)		0	$ (2,173,000)
Short [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Derivative Asset	[1]	748,000		2,450,000
Unrealized Derivative Liability	[1]	(1,417,000)		(2,951,000)
Long [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Derivative Asset	[1]	21,000		50,000
Unrealized Derivative Liability	[1]	(36,000)		(90,000)
Fair Value, Inputs, Level 1 [Member] | Short [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Derivative Asset		0		44,000
Unrealized Derivative Liability		(10,000)		0
Fair Value, Inputs, Level 1 [Member] | Long [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Derivative Asset		0		0
Unrealized Derivative Liability		0		0
Fair Value, Inputs, Level 2 [Member] | Short [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Derivative Asset		748,000		2,406,000
Unrealized Derivative Liability		(1,407,000)		(2,951,000)
Fair Value, Inputs, Level 2 [Member] | Long [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Derivative Asset		21,000		50,000
Unrealized Derivative Liability		(36,000)		(90,000)
Fair Value, Inputs, Level 3 [Member] | Short [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Derivative Asset		0		0
Unrealized Derivative Liability		0		0
Fair Value, Inputs, Level 3 [Member] | Long [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Derivative Asset		0		0
Unrealized Derivative Liability		0		0
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Inventories Carried At Market	[2]	5,945,000		7,713,000
Contingent Consideration		(21,010,000)	[3]	0
Embedded Derivative	[4]	3,409,000		3,409,000
Fair Value, Measurements, Recurring [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Gain (Loss) on Derivatives	[5]	311,000		1,026,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Inventories Carried At Market		0	[2]	0
Contingent Consideration		0		0
Embedded Derivative		0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Gain (Loss) on Derivatives	[5]	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Inventories Carried At Market		5,945,000	[2]	7,713,000
Contingent Consideration		0		0
Embedded Derivative		0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Gain (Loss) on Derivatives	[5]	311,000		1,026,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Inventories Carried At Market		0	[2]	0
Contingent Consideration		(21,010,000)		0
Embedded Derivative		3,409,000		3,409,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Gain (Loss) on Derivatives	[5]	$ 0		$ 0

[1] U nrealized short-term derivative asset is included in prepaid expenses and other current assets, u nrealized long-term derivative asset is included in other assets, unrealized short-term derivative liability is included in o ther current liabilities and u nrealized long-term derivative liability is included in long-term liabilities on the consolidated balance sheets.

[2] Inventories car ried at market are included in in ventories on the consolidated balance sheets.

[3] Contingent consideration obligations are included in long-term liabilities (including the current portion thereof) on the consolidated balance sheets.

[4] The embedded derivative is included in other long term assets on the consolidated balance sheets.

[5] The forward fo reign currency contracts are included in accounts receivable on the consolidated balance sheets.