Collaboration arrangements (Details) (USD $) In Millions, except Share data, unless otherwise specified	Mar. 29, 2014
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Marketable Securities, Noncurrent	$ 17.9
Transition Therapeutics [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Marketable Securities, Noncurrent	$ 15.0
Investment Owned, Balance, Shares	2,255,640

Balance held at close of period in number of shares.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 946

-SubTopic 320

-Section S99

-Paragraph 4

-Subparagraph (SX 210.12-12C.Column B)

-URI http://asc.fasb.org/extlink&oid=6955306&loc=d3e611225-123010

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 946

-SubTopic 320

-Section S99

-Paragraph 6

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-URI http://asc.fasb.org/extlink&oid=6955306&loc=d3e611322-123010

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 946

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-Section S99

-Paragraph 1

-Subparagraph (SX 210.12-12.Column B)

-URI http://asc.fasb.org/extlink&oid=6955306&loc=d3e611133-123010

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 12C

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-Article 12

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant