Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2024	Nov. 05, 2024
Document and Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2024
Document Transition Report	false
Securities Act File Number	001-36576
Entity Registrant Name	MARINUS PHARMACEUTICALS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-0198082
Entity Address, Address Line One	5 Radnor Corporate Center, Suite 500
Entity Address, Address Line Two	100 Matsonford Rd
Entity Address, City or Town	Radnor
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19087
City Area Code	484
Local Phone Number	801-4670
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	MRNS
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		55,185,622
Entity Central Index Key	0001267813
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q3
Amendment Flag	false