Commitments and Contitngencies - Long-Term Time Charters-Additional Information (Details) - Long-term time charters (including charter agreements vessels under construction) [Member]	6 Months Ended
Jun. 30, 2015
Time charter arrangements remaining terms period	up to 105 months
Revenue days per annum	365 Days
Redelivery dates	earliest possible redelivery dates

The remaining terms period (in total months) of the contracted time charter agreements, including the contracted time charter agreements of vessels under construction, from the end of the reporting period.

No definition available.

Name:	cmre_TimeCharterArrangementsRemainingTermsPeriod
Namespace Prefix:	cmre_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration