Net loss per share (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended						1 Months Ended	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013 Stock options	Mar. 31, 2012 Stock options	Mar. 31, 2013 4.75% Senior Notes	Mar. 31, 2012 4.75% Senior Notes	Dec. 31, 2012 Pfizer Note due 2013	Mar. 31, 2012 Pfizer Note due 2013	Mar. 31, 2013 Pfizer Note due 2014	Mar. 31, 2012 Pfizer Note due 2014
Anti-dilutive securities
Interest rate of debt (as a percent)					4.75%	4.75%
Potential common shares excluded from diluted net loss per share computation	70,818,118	72,800,409	24,208,663	24,729,232	45,583,814	45,584,040		1,461,496	1,025,641	1,025,641
Aggregate principal amount of notes to be converted							$ 10.0
Common stock issued in conversion of notes (in shares)							1,461,496