Restructuring Costs - Summary of Restructuring Activities (Detail) $ in Thousands	3 Months Ended
Mar. 31, 2017 USD ($)
Restructuring Cost and Reserve [Line Items]
Accrual, Beginning balance	$ 763
Accrual, Ending balance	495
PNT2258 [Member]
Restructuring Cost and Reserve [Line Items]
Accrual, Beginning balance	763
Cash payments	(223)
Accrual, Ending balance	495
PNT2258 [Member] \| Contract Termination [Member]
Restructuring Cost and Reserve [Line Items]
Accrual, Beginning balance	664
Cash payments	(130)
Accrual, Ending balance	489
PNT2258 [Member] \| Employee Termination [Member]
Restructuring Cost and Reserve [Line Items]
Accrual, Beginning balance	99
Cash payments	(93)
Accrual, Ending balance	6
Research and development [Member] \| PNT2258 [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring cost	(45)
Research and development [Member] \| PNT2258 [Member] \| Contract Termination [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring cost	$ (45)

Carrying amount as of the balance sheet date of known and estimated obligations associated with exit from or disposal of business activities or restructurings pursuant to a duly authorized plan, which are expected to be paid in the next twelve months or in the normal operating cycle if longer. Costs of such activities include those for one-time termination benefits, termination of an operating lease or other contract, consolidating or closing facilities, relocating employees, and costs associated with an ongoing benefit arrangement, but excludes costs associated with the retirement of a long-lived asset.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 5.P.4(b)(2))
-URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869

Name:	us-gaap_RestructuringReserveCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant