Organization and Summary of Significant Accounting Policies (Details) (USD $)	3 Months Ended			1 Months Ended			1 Months Ended		3 Months Ended				3 Months Ended
	Mar. 31, 2013 item	Mar. 31, 2012	Dec. 31, 2012	Jun. 30, 2012 Private company 1, Cost Method Investment	Mar. 31, 2013 Private company 1, Cost Method Investment	Dec. 31, 2012 Private company 1, Cost Method Investment	Oct. 31, 2012 Private company 2	Aug. 31, 2012 Private company 2	Mar. 31, 2013 Private company 2	Dec. 31, 2012 Private company 2	Mar. 31, 2011 Private company 2	Dec. 31, 2010 Private company 1, Equity Method Investment	Mar. 31, 2013 Genomic Health International Holdings, LLC item
Organization and summary of significant accounting policies
Number of wholly-owned subsidiaries	3												3
Revenue Recognition
Minimum number of Oncotype DX tests by exclusive distribution agreements	1
Approximate number of distributors with exclusive distribution agreements	20
Minimum number of countries covered for distribution agreements establishment	80
Accrued refunds	$ 663,000		$ 664,000
Allowance for Doubtful Accounts
Allowance for doubtful accounts	1,393,000		1,133,000
Write-offs for doubtful accounts recorded against allowance	1,000,000	928,000
Bad debt expense	1,300,000	689,000
Investments in Privately Held Companies
Amount invested in preferred stock of a private company												500,000
Percentage of ownership interest in private company												21.00%
Additional investment made in preferred stock of a private company				400,000			3,600,000	1,000,000
Percentage of ownership interest in private company accounted for under the cost method of accounting				16.00%				19.00%		18.00%
Investment in redeemable preferred stock											2,300,000
Investment in the redeemable preferred stock of a private company, percent of the entity's outstanding voting shares											21.00%
Carrying value of investment in the preferred stock of a private company										6,900,000
Carrying value of investments in privately held companies	7,500,000		7,500,000		643,000	643,000			6,900,000
Impairment of investment in the preferred stock of a private company									$ 0