Quarterly report pursuant to Section 13 or 15(d)

Mack-Cali Realty Corporation Stockholders' Equity And Mack-Cali Realty, L.P.'s Partners' Capital (Share/Unit Repurchase Program And Dividend Reinvestment And Stock Purchase Plan) (Narrative) (Details)

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Mack-Cali Realty Corporation Stockholders' Equity And Mack-Cali Realty, L.P.'s Partners' Capital (Share/Unit Repurchase Program And Dividend Reinvestment And Stock Purchase Plan) (Narrative) (Details) - USD ($)
 6 Months Ended 12 Months Ended
Jun. 30, 2020
Dec. 31, 2012
Stockolders Equity [Line Items]    
Date share repurchase program was initiated September 2012  
Capacity of share repurchase program $ 150,000,000  
Shares purchased and retired 394,625  
Aggregate cost of stock repurchased $ 11,000,000  
Capacity available for additional repurchase of outstanding common stock $ 139,000,000  
Proceeds from sale of common units   $ 11,000,000
Dividend Reinvestment And Stock Purchase Plan [Member]    
Stockolders Equity [Line Items]    
Common stock reserved for future issuance 5,500,000  
Monthly cash investment without restriction, maximum $ 5,000