Amount charged to advertising expense for the period, which are expenses incurred with the objective of increasing revenue for a specified brand, product or product line.

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

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 93-7

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 720

-SubTopic 35

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6420018&loc=d3e36677-107848

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

Summary of significant accounting policies (Details 6) (USD $) In Millions, unless otherwise specified	12 Months Ended			1 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Jan. 31, 2012 Collaborative arrangements Musculoskeletal Transplant Foundation ("MTF") Y	Dec. 31, 2009 Collaborative arrangements Musculoskeletal Transplant Foundation ("MTF") Y
Summary of significant accounting policies
Period of agreement with MTF (in years)					10
Extended Period of existing agreement with MTF (in years)				5
Advertising expense	$ 0.5	$ 0.6	$ 0.7
Income taxes
Unrecognized tax benefits inclusive of interest and penalties	$ 1.2	$ 1.0