Major Customers, Partnerships and Strategic Alliances - California Institute for Regenerative Medicine - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	1 Months Ended	3 Months Ended		1 Months Ended	3 Months Ended
	Mar. 31, 2014	Oct. 31, 2009 California Institute for Regenerative Medicine [Member]	Mar. 31, 2014 California Institute for Regenerative Medicine [Member]	Mar. 31, 2013 California Institute for Regenerative Medicine [Member]	May 31, 2013 California Institute for Regenerative Medicine [Member] Beta-thalassemia [Member]	Mar. 31, 2014 California Institute for Regenerative Medicine [Member] Beta-thalassemia [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Funds due under the agreement		$ 14.5			$ 6.4
Agreement to receive		4 years			4 years
Expected amount to be received for research and development		5.2
Agreement date		Oct. 31, 2009
Receivables from sale against the grant funded to entity from sale of product	Two times the amount Sangamo receives in funding under the agreement
Revenues under agreement						0.4
Collaboration agreement related costs and expenses			$ 0.3	$ 0.4		$ 1.3