Non-Controlling Interests - Spero Potentiator - Additional Information (Detail) - USD ($)	1 Months Ended
	Jun. 30, 2017	Aug. 31, 2016	Jan. 31, 2016	Nov. 30, 2015	Feb. 28, 2015	Sep. 30, 2018	Dec. 31, 2017
Noncontrolling Interest [Line Items]
Non-controlling interest						$ 355,000	$ 355,000
Spero Potentiator, Inc. [Member]
Noncontrolling Interest [Line Items]
Common stock shares issued		2,160	2,160	2,736
Proceeds from the issuance of common stock, net of issuance costs		$ 0	$ 0	$ 0
Non-controlling interest						$ 0
Spero Potentiator, Inc. [Member] | Anti- dilution Rights [Member]
Noncontrolling Interest [Line Items]
Fair value of derivative liability					$ 2,400,000
Spero Potentiator, Inc. [Member] | Northern Antibiotics Oy Ltd. [Member]
Noncontrolling Interest [Line Items]
Common stock shares issued					996
Common stock issued, aggregate fair value					$ 1,100,000
Increase in non-controlling interest and reduction of derivative liability		$ 1,000,000	$ 1,000,000	$ 1,500,000
Cash payment for repurchase of shares	$ 1,000,000
Contingent consideration	100,000
Milestone payments	7,000,000
Cash payment for repurchase of shares	2,500,000
Non-controlling interest	6,400,000
Increase to accumulated deficit	$ 1,000,000
Spero Potentiator, Inc. [Member] | Northern Antibiotics Oy Ltd. [Member] | Anti- dilution Rights [Member]
Noncontrolling Interest [Line Items]
Ownership percentage					49.90%
Proceeds from the issuance of common stock, net of issuance costs					$ 0