Strategic Alliances (Details) - USD ($)							1 Months Ended			3 Months Ended			12 Months Ended	99 Months Ended
	Mar. 08, 2023	Sep. 14, 2021	Jul. 06, 2021	Jun. 18, 2021	May 05, 2020	Oct. 21, 2019	Sep. 30, 2021	May 31, 2016	Jan. 31, 2015	Mar. 31, 2023	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2022	Mar. 31, 2023
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment received										$ 237,577,000		$ 329,219,000
Accrued expenses										106,058,000			$ 98,269,000	$ 106,058,000
Contract liability										140,000			138,000	140,000
Milestone revenue recognized										(2,000)
Transfer of intellectual property and other
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment received										64,826,000		5,962,000
Product | Transfer of intellectual property and other | First Marketing Approval in Europe
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment received					$ 3,000,000
Product | Transfer of intellectual property and other | Germany Price Approval by Local Sick Fund Association
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment received					7,000,000
Merck | Other License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment received	$ 50,000,000									50,000,000
Development milestone payments	$ 872,500,000
Accrued expenses										12,500,000				12,500,000
LeaderMed | LeaderMed Joint Venture | Corporate Joint Venture
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Ownership interest in joint venture (as a percent)		47.00%					47.00%
Initial investment in joint venture		$ 11,000,000
Ownership percentage by related parties (as a percent)		53.00%
LeaderMed | LeaderMed Joint Venture | Corporate Joint Venture | Transfer of intellectual property and other
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment received		$ 1,000,000					$ 1,000,000
CAMP4
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment (in shares)			3,373,008
Outstanding shares (as a percent)			9.00%
Period following first commercial sale in a country			10 years
CAMP4 | Transfer of intellectual property and other
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment received			$ 1,500,000
CAMP4 | Dravet Syndrome Products
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Development milestone payments			3,500,000
Sales milestone payments			$ 90,000,000
Development milestone payments (in shares)			5,782,299
CAMP4 | Non-Dravet Syndrome Products
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Development milestone payments			$ 4,000,000
Sales milestone payments			$ 90,000,000
Development milestone payments (in shares)			1,082,248
Nicoya
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment from development and license agreement				$ 5,000,000
Proceeds including accrued interest for delayed payment				2,500,000
Proceeds from submission of investigational new drug				$ 2,500,000
Period after first commercial sale				10 years
Nicoya | Phase Three Initiation
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment from development and license agreement				$ 5,000,000
Nicoya | Regulatory and Development
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestone payment from development and license agreement				$ 115,000,000
Nicoya | Product | Transfer of intellectual property and other
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Maximum milestone payments										2,500,000
Vifor | Exclusive Option
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Maximum milestone payments								$ 555,000,000
Vifor | Product | Transfer of intellectual property and other
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment received										7,000,000		3,000,000
Maximum milestone payments										7,000,000
EirGen Pharma Limited | Regulatory Milestones
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Maximum milestone payments					10,000,000
EirGen Pharma Limited | Sales Milestones
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Maximum milestone payments					$ 207,000,000
Pfizer | Product
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Maximum milestone payments									$ 275,000,000		$ 85,000,000
Each milestone payment													85,000,000
Annual height velocity at point in time						12 months
Initial upfront payment									295,000,000
Contract liability										0			$ 0	0
Milestone revenue recognized														$ 85,000,000
Pfizer | Product | Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Each milestone payment									20,000,000
Pfizer | Product | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Each milestone payment									$ 90,000,000
Pfizer | Product | Transfer of intellectual property and other
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment received										$ 1,800,000		$ 2,200,000