Subsequent Events (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended	1 Months Ended	12 Months Ended
	Dec. 31, 2011	Feb. 29, 2012 Oakbrook Terrace Lease [Member]	Dec. 31, 2011 Pfizer Collaboration Agreement [Member] days
Subsequent Event [Line Items]
Number of days remaining for winding down collaboration activities			180
Deferred revenue balance			$ 72.0
Lease agreement for office space located in square feet	3,700	15,336
Annual non-cancelable rent payments		0.3
Letter of credit collateralized by restricted cash		$ 0.8