Sanofi - Additional Information (Detail) (Sanofi, USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
Sanofi
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Initial upfront non-refundable payment	$ 35
Additional non-refundable payment	5
Development, regulatory and commercial contingent payments	250
Maximum days to participate in development and promotion of products	90 days
Upfront payment being recognized	$ 40