Amount of impairment loss resulting from write-down of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit to fair value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16373-109275

Name:	us-gaap_ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Goodwill and intangible assets Goodwill and intangible assets - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Oct. 01, 2016	Oct. 01, 2016	Oct. 03, 2015
Indefinite-lived Intangible Assets [Line Items]
Intangible assets impaired during the period		$ 47,905	$ 0
Tradenames [Member]
Indefinite-lived Intangible Assets [Line Items]
Intangible assets impaired during the period		$ 47,905
Selling, general and administrative expenses [Member] \| Tradenames [Member]
Indefinite-lived Intangible Assets [Line Items]
Intangible assets impaired during the period	$ 47,905