Commitments And Contingencies (Ground Lease Agreements) (Narrative) (Details) - USD ($)	3 Months Ended	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Commitments And Contingencies [Abstract]
Ground lease expense incurred	$ 599,000	$ 128,000	$ 1,200,000	$ 229,000

Operating Lease, Expense, Including Sublease Rentals

No definition available.

Name:	cli_OperatingLeaseExpenseIncludingSubleaseRentals
Namespace Prefix:	cli_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration