Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)		3 Months Ended	9 Months Ended
	Aug. 01, 2016	Sep. 30, 2017	Sep. 30, 2017	Mar. 31, 2016	Mar. 21, 2016
Summary Of Significant Accounting Policies [Line Items]
Deferred revenue, current, related to contrave net sales		$ 700,000	$ 700,000
Impairment of finite-lived intangible assets			0
Percentage of estimated product returns		1.00%
Decreased percentage of estimated product returns		0.50%
Decrease in product returns expense		$ 800,000
Increase (decrease) in net loss per share due to adjustment of product returns expense		$ (0.05)
Percentage of assumed liability	1.00%	0.50%
Adjustment to general and administrative expense		$ 1,100,000	1,100,000
Increase (decrease) in net loss per share due to adjustment of general and administrative expense		$ (0.07)
Increase in rebate expense		$ 847,000
Increase (decrease) in net loss per share due to adjustment of rebate expense		$ 0.05
Accounting Standards Update 2016-09 - Improvements to Employee Share-Based Payment Accounting
Summary Of Significant Accounting Policies [Line Items]
Additional deferred tax assets offset by valuation allowance		$ 4,600,000	$ 4,600,000
Takeda Pharmaceutical Company Limited
Summary Of Significant Accounting Policies [Line Items]
Percentage of product return		1.00%
0% Convertible Senior Secured Notes due 2020 (2016 Notes)
Summary Of Significant Accounting Policies [Line Items]
Interest rate		0.00%	0.00%	0.00%	0.00%
June 21, 2017
Summary Of Significant Accounting Policies [Line Items]
Restricted cash and investment		$ 40,000,000	$ 40,000,000