Legal Matters (Details) (License Agreement With Genentech [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 Percent
License Agreement With Genentech [Member]
Loss Contingencies [Line Items]
Amount of payment to be made upon reaching minimum sales target	$ 60
Cumulative sales range, minimum	400
Royalty payment percentage of cumulative sales within cumulative sales range (in hundredths)	4.75%
Cumulative sales range, maximum	$ 3,000
Royalty payment percentage of cumulative sales over range (in hundredths)	5.50%