Subsequent Events (Details) (Governance agreement, GSK, Common stock, USD $) In Millions, except Share data, unless otherwise specified	9 Months Ended	1 Months Ended
	Sep. 30, 2014	Nov. 30, 2014 Subsequent events Future
Subsequent events
Common stock to be purchased (in shares)	832,650	832,456
Common stock to be purchased, aggregate purchase price	$ 25.3	$ 12.8