Summary of Significant Accounting Policies (Narrative) (Details) $ in Millions	6 Months Ended
Jun. 30, 2021 USD ($)
Accounting Policies [Abstract]
Lease rent deferred	$ 3.5
Lease rent deferrals continued to recognize rental income	2.4
Lease rent waived	$ 2.4

Lease rent deferrals continued to recognize rental income.

No definition available.

Name:	cdr_LeaseRentDeferralsContinuedToRecognizeRentalIncome
Namespace Prefix:	cdr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant