License and Development Agreements (Details) (Collaborative agreement, Roche, USD $) In Millions, unless otherwise specified	1 Months Ended	3 Months Ended	12 Months Ended			24 Months Ended
	Jan. 31, 2009	Dec. 31, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Collaborative agreement | Roche
License and Development Agreements
Non-refundable upfront license payment received	$ 16
Initial term for research	2 years
Amount received related to research and development support						21.2
Accelerated recognition of remaining deferred revenue from upfront payment		2.1
License revenue recognized			0	0	6.7
Cost sharing revenue recognized			$ 0	$ 0	$ 0