Significant Collaborative Research and Development Agreements - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended		12 Months Ended
	Jun. 30, 2010	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Mitsubishi Tanabe
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up-front license fees						$ 30,000,000
Collaborative agreement maximum additional payment to receive						85,000,000
Patent rights period		The longer of ten years or the life of the related patent rights.
Collaborative arrangement right description		Under the terms of the Company’s agreement with Mitsubishi Tanabe, the collaboration effort between the parties to advance INGREZZA towards commercialization in Japan and other select Asian markets is governed by a joint steering committee and joint development committee with representatives from both the Company and Mitsubishi Tanabe. There are no performance, cancellation, termination or refund provisions in the agreement that would have a material financial consequence to the Company. The Company does not directly control when event-based payments will be achieved or when royalty payments will begin. Mitsubishi Tanabe may terminate the agreement at its discretion upon 180 days’ written notice to the Company. In such event, all INGREZZA product rights for Japan and other select Asian markets would revert to the Company.
Collaboration termination notice period		180 days
Revenues recognized under collaboration agreement		$ 0	$ 0	$ 15,000,000		19,800,000
Deferred revenues under collaboration						$ 10,200,000
Mitsubishi Tanabe | Topic 606
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Clinical trial cost		12,000,000
Up-front consideration received		$ 30,000,000
AbbVie
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up-front license fees	$ 75,000,000
Patent rights period		Ten years or the life of the related patent rights.
Collaborative arrangement right description		The Company will be entitled to a percentage of worldwide sales of GnRH Compounds for the longer of ten years or the life of the related patent rights.
Collaboration termination notice period		180 days
Revenues recognized under collaboration agreement		$ 0	$ 0	$ 30,000,000	$ 15,000,000
AbbVie | Development and Regulatory Milestone Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborative agreement maximum additional payment to receive		480,000,000
Collaborative agreement payment received		75,000,000
AbbVie | Commercial Milestone Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborative agreement maximum additional payment to receive		50,000,000
AbbVie | Topic 606
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up-front consideration received		$ 75,000,000