License agreement with Wyeth Holding Corporation (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Sep. 30, 2015
Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Increase In Milestone Payment	$ 15.0
Increase In License Maintenance Fees	0.3
Minimum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Increase In Milestone Payment	14.0
Increase In License Maintenance Fees	0.2
License agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate amount of payments made under license agreement	$ 7.6
License agreement | Wyeth
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Accrued milestone payment associated with the first Phase 3 clinical trial		$ 3.0