Roche License Agreements (Details) (USD $)	12 Months Ended	1 Months Ended
	Dec. 31, 2014	May 31, 2014	Feb. 28, 2014
Collaborative Arrangement [Member]
License Agreement [Line Items]
Portion of revenue and expenses attributable to company, percentage	30.00%
Collaborative Arrangement [Member] | Roche [Member]
License Agreement [Line Items]
Milestone Payment Received, Clinical Milestone		$ 15,000,000
Cost sharing payments Recognized As Research And Development Expense	1,400,000
Potential payment upon achievement of development, regulatory and various first commercial sales milestones	380,000,000
Potential payment for achievement of non U.S.commercial sales milestones	175,000,000
Potential alternative commercial sales milestone payment	155,000,000
Portion of revenue and expenses attributable to company, percentage	70.00%
Multiple Element Consideration, Relative Sales Price Method, Amt Allocable to License	35,600,000
Development Reimbursement	6,000,000
Milestone payment recognized as Collaboration Revenue	13,300,000
Milestone Payment Used To Offset Research and Development Expense	1,700,000
Research Reimbursement [Member] | Roche [Member]
License Agreement [Line Items]
Collaboration Service Revenue, Research Services	1,700,000
Development Costs Reimbursement [Member] | Roche [Member]
License Agreement [Line Items]
Development Reimbursement Recognized as Collaboration License Revenue	5,300,000
Development Reimbursement Recognized As Offset To Research And Development Expense	700,000
License [Member] | Roche [Member]
License Agreement [Line Items]
Upfront Payment pursuant to License Agreement			$ 30,000,000