Fair Value Measurements (Details 2) (USD $) In Thousands	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010
Summary of the changes in the fair value of the non-current liability for contingent consideration:
Fair value at beginning of period	$ 253,458	$ 200,528
Payments	(535,000)	(40,000)
Increase in fair value of the non-current liability for contingent consideration	17,250	95,485
Fair value at end of period	$ 270,708	$ 256,013

Changes in fair value of liability for contingent consideration non current.

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Namespace Prefix:	onxx
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of potential cash payments that could result from the contingent consideration arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141
-Paragraph 51
-Subparagraph f
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ Details

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Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
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- Definition

This element represents a liability measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19207-110258

+ Details

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