Mack-Cali Realty Corporation Stockholders' Equity And Mack-Cali Realty, L.P.'s Partners' Capital (Schedule Of General Partner Capital) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Investment Company, Financial Highlights [Line Items]
Balance	$ 1,398,817
Common stock distributions		$ (2,270)
Redeemable noncontrolling interests	(6,471)	(6,471)
Redemption of common units	(10,459)	(2,141)
Directors' deferred compensation plan	72	82
Cancellation of common stock, value	(118)
Other comprehensive income (loss)		(16)
Balance	1,406,823
General Partner Common Unitholders [Member]
Investment Company, Financial Highlights [Line Items]
Balance	1,398,817	1,493,699
Net income (loss) available to common shareholders	7,623	(39,924)
Common stock distributions		(18,119)
Redeemable noncontrolling interests	(1,791)	(2,804)
Shares issued under Dividend Reinvestment and Stock Purchase Plan	18	19
Directors' deferred compensation plan	72	82
Stock compensation	646	430
Cancellation of common stock, value	(118)
Other comprehensive income (loss)		18
Rebalancing of ownership percent between parent and subsidiaries	1,556	742
Balance	$ 1,406,823	$ 1,434,143