Basis of Presentation and General information, General Information (Details)	Dec. 31, 2020
Thalassa [Member] \| Series B Preferred Shares [Member]
Basis of Presentation [Abstract]
Percentage of shares held	100.00%

Percentage of the Company's shares held by another entity.

No definition available.

Name:	ctrm_PercentageOfSharesHeld
Namespace Prefix:	ctrm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant