Organization and Summary of Significant Accounting Policies (Principles of Consolidation) (Details)	9 Months Ended
Sep. 30, 2017 subsidiary
Principles of Consolidation
Number of wholly-owned subsidiaries	2
Genomic Health International Holdings, LLC
Principles of Consolidation
Number of wholly-owned subsidiaries	9

Represents the number of wholly owned subsidiaries of the entity.

No definition available.

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Namespace Prefix:	ghdx_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration