For an unclassified balance sheet, amounts due from related parties including affiliates, employees, joint ventures, officers and stockholders, immediate families thereof, and pension funds.

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Carrying amount as of the balance sheet date of obligations due all related parties.

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Related Party Transactions - Additional Information (Detail) (USD $)	12 Months Ended			73 Months Ended	12 Months Ended	61 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Dec. 31, 2011	Dec. 31, 2013
Amunix Inc. [Member]
Related Party Transaction [Line Items]
Additional consideration, milestone payments		$ 30,000,000
Operating expenses from related party transaction	0	0	74,000	7,400,000
Amounts receivable	0			0
Amounts payable	0			0
Amunix Inc. [Member] \| Preferred stock [Member]
Related Party Transaction [Line Items]
Ownership Percentage		10.00%				10.00%
Index Ventures [Member] \| Preferred stock [Member]
Related Party Transaction [Line Items]
Ownership Percentage		24.00%				24.00%
Mark de Boer [Member]
Related Party Transaction [Line Items]
Consulting fees			0			120,000
Accelerated vesting of shares of common stock					10,185
Additional stock compensation expense related to accelerated vesting					1,000
Diartis [Member]
Related Party Transaction [Line Items]
Operating expenses from related party transaction	0	0	1,400,000	3,900,000
Amounts receivable	0	0		0		0
Third Parties [Member]
Related Party Transaction [Line Items]
Amounts payable	$ 0	$ 0		$ 0		$ 0