Annual report pursuant to Section 13 and 15(d)

Document And Entity Information

Document And Entity Information - USD ($)
12 Months Ended
Dec. 31, 2020
Feb. 23, 2021
Jun. 30, 2020
Document Type 10-K    
Amendment Flag false    
Document Annual Report true    
Document Transition Report false    
Document Period End Date Dec. 31, 2020    
Entity Central Index Key 0000924901    
Current Fiscal Year End Date --12-31    
Document Fiscal Year Focus 2020    
Document Fiscal Period Focus FY    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Public Float     $ 1,314,998,454
Entity File Number 1-13274    
Entity Incorporation, State or Country Code MD    
Entity Tax Identification Number 22-3305147    
Entity Address, Address Line One Harborside 3, 210 Hudson St.    
Entity Address, Address Line Two Ste. 400    
Entity Address, City or Town Jersey City    
Entity Address, State or Province NJ    
Entity Address, Postal Zip Code 07311    
City Area Code 732    
Local Phone Number 590-1010    
Title of 12(b) Security Common Stock, $0.01 par value    
Trading Symbol CLI    
Security Exchange Name NYSE    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
Entity Shell Company false    
Entity Common Stock, Shares Outstanding   90,729,044  
ICFR Auditor Attestation Flag true    
Documents incorporated by reference DOCUMENTS INCORPORATED BY REFERENCE:  Portions of the Mack-Cali Realty Corporation’s definitive proxy statement for fiscal year ended December 31, 2020 to be issued in conjunction with the registrant’s annual meeting of shareholders expected to be held on June 9, 2021 are incorporated by reference in Part III of this Form 10-K.  The definitive proxy statement will be filed by the registrant with the SEC not later than 120 days from the end of the registrant’s fiscal year ended December 31, 2020.    
Mack-Cali Realty LP [Member]      
Entity Registrant Name MACK-CALI REALTY, L.P.    
Entity File Number 333-57103