Unsecured Revolving Credit Facility And Term Loans (Schedule Of Interest Rate On Outstanding Borrowings Payable) (Details) - 2016 Term Loan [Member]	12 Months Ended
	Dec. 31, 2017
Line of Credit Facility [Line Items]
Interest Rate - Applicable Basis Points Above LIBOR	1.40%
Mack-Cali Realty LP [Member] | No Ratings Or Less Than Baa3 [Member] | No Ratings Or Less Than BBB- [Member]
Line of Credit Facility [Line Items]
Unsecured Debt Ratings	No ratings or less than BBB-/Baa3
Interest Rate - Applicable Basis Points Above LIBOR	1.85%
Mack-Cali Realty LP [Member] | Baa3 [Member] | BBB- [Member]
Line of Credit Facility [Line Items]
Unsecured Debt Ratings	BBB- or Baa3 (current interest rate based on Company's election)
Interest Rate - Applicable Basis Points Above LIBOR	1.40%
Mack-Cali Realty LP [Member] | Baa2 [Member] | BBB [Member]
Line of Credit Facility [Line Items]
Unsecured Debt Ratings	BBB or Baa2
Interest Rate - Applicable Basis Points Above LIBOR	1.15%
Mack-Cali Realty LP [Member] | Baa1 [Member] | BBB+ [Member]
Line of Credit Facility [Line Items]
Unsecured Debt Ratings	BBB+ or Baa1
Interest Rate - Applicable Basis Points Above LIBOR	1.00%
Mack-Cali Realty LP [Member] | A3 Or Higher [Member] | A- Or Higher [Member]
Line of Credit Facility [Line Items]
Unsecured Debt Ratings	A- or A3 or higher
Interest Rate - Applicable Basis Points Above LIBOR	0.90%