License agreement with Wyeth Holding Corporation (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($)
Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Increase In Milestone Payment	$ 15.0
Minimum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Increase In Milestone Payment	$ 14.0
License agreement | Wyeth
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Notice period required for termination of license agreement	90 days
Aggregate amount of payments made under license agreement	$ 7.3
Accrued milestone payment associated with the first Phase 3 clinical trial	3.0
License agreement | Wyeth | Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Increase In License Maintenance Fees	0.3
License agreement | Wyeth | Minimum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Increase In License Maintenance Fees	$ 0.2