| Document And Entity Information | Nov. 03, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Nov. 3, 2021 |
| Entity Registrant Name | MACK-CALI REALTY CORPORATION |
| Entity Incorporation, State or Country Code | MD |
| Entity File Number | 1-13274 |
| 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Title of 12(b) Security | Common Stock, par value $0.01 |
| Trading Symbol | CLI |
| Security Exchange Name | NYSE |
| Amendment Flag | false |
| Entity Central Index Key | 0000924901 |
