License agreement with Wyeth Holding Corporation (Narrative) (Details) $ in Millions	9 Months Ended
	Sep. 30, 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]
Aggregate amount of payments made under license agreement	7.6
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