Annual report pursuant to Section 13 and 15(d)

Document And Entity Information

Document And Entity Information - USD ($)
12 Months Ended
Dec. 31, 2018
Mar. 01, 2019
Jun. 29, 2018
Document Information [Line Items]      
Entity Registrant Name SEACOR Marine Holdings Inc.    
Entity Central Index Key 0001690334    
Trading Symbol smhi    
Current Fiscal Year End Date --12-31    
Entity Filer Category Accelerated Filer    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Well-known Seasoned Issuer No    
Entity Emerging Growth Company true    
Entity Small Business false    
Entity Common Stock, Shares Outstanding (in shares)   21,043,080  
Entity Public Float     $ 437,851,121
Document Type 10-K    
Document Period End Date Dec. 31, 2018    
Document Fiscal Year Focus 2018    
Document Fiscal Period Focus FY    
Amendment Flag false    
Entity Shell Company false    
Entity Ex Transition Period true