Mortgage and Other Indebtedness, Net - Narrative (Details)	1 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended
	May 31, 2019 USD ($)	Jun. 30, 2019 USD ($)	Sep. 30, 2019 USD ($) associated_center mall subsidiary mortgage_note_receivable	Dec. 31, 2018 USD ($) unsecured_term_loan	Apr. 30, 2019 USD ($)	Jan. 31, 2019 USD ($)	Jan. 01, 2019 USD ($)	Jan. 01, 2018 USD ($)
Debt Instrument [Line Items]
Number of malls securing the credit facility | mall			17
Number of associated centers securing the credit facility | associated_center			3
Number of wholly owned subsidiaries | subsidiary			36
Ownership interest in guarantor subsidiaries by Operating Partnership (as a percent)			100.00%
Ownership interest by noncontrolling owners (as a percent)			35.00%
Principal maturities for remainder of fiscal year			$ 117,948,000
Principal maturities for remainder of fiscal year Related to maturing operating property loans			$ 97,323,000
Weighted-average maturity period			4 years	3 years 8 months 12 days
Unsecured lines of credit
Debt Instrument [Line Items]
Number of debt instruments | unsecured_term_loan				3
Maximum borrowing capacity				$ 1,100,000,000
Unsecured term loans
Debt Instrument [Line Items]
Total Outstanding				$ 695,000,000		$ 500,000,000
Number of debt instruments | unsecured_term_loan				3
Secured line of credit
Debt Instrument [Line Items]
Variable-rate debt, amount			$ 304,769,000
Non-recourse loans on operating properties
Debt Instrument [Line Items]
Total Outstanding			163,476,000
Default minimum of debt instrument			50,000,000
Secured term loan
Debt Instrument [Line Items]
Variable-rate debt, amount			$ 473,750,000
Volusia Mall | Mortgages
Debt Instrument [Line Items]
Total Outstanding		$ 41,000,000			$ 50,000,000
Stated interest rate (as a percent)		4.56%			8.00%
Outlet Shoppes at Laredo | Mortgages
Debt Instrument [Line Items]
Total Outstanding	$ 43,000,000
Early repayment of debt	$ 10,800,000
Guarantor Subsidiaries
Debt Instrument [Line Items]
Number of malls securing the credit facility | mall			17
Number of associated centers securing the credit facility | associated_center			3
Number of wholly owned subsidiaries | subsidiary			36
Number of malls not classified as collateral for the secured credit facility | mall			5
Number of associated centers not classified as collateral for the secured credit facility | associated_center			2
Number of mortgage notes receivable not classified as collateral for the secured credit facility | mortgage_note_receivable			4
Principal maturities for remainder of fiscal year			$ 66,757,000
Weighted-average maturity period			1 year 7 months 6 days	1 year 1 month 6 days
Guarantor Subsidiaries | Mortgages
Debt Instrument [Line Items]
Total Outstanding								$ 37,295,000
Interest rate (as a percent)								5.75%
LIBOR | Unsecured Term Loan 1
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)		0.0225%
Secured Debt | Line of Credit
Debt Instrument [Line Items]
Total Outstanding							$ 1,185,000,000
Interest rate (as a percent)			4.35%
Quarterly installment payments on debt							35,000,000
Secured Debt | Line of Credit | Minimum
Debt Instrument [Line Items]
Annual facility fee (as a percent)			0.25%
Secured Debt | Line of Credit | Maximum
Debt Instrument [Line Items]
Annual facility fee (as a percent)			0.35%
Secured Debt | Unsecured term loans
Debt Instrument [Line Items]
Total Outstanding							500,000,000
Secured Debt | Revolving Credit Facility
Debt Instrument [Line Items]
Total Outstanding							685,000,000
Secured Debt | Guarantor Subsidiaries | Line of Credit
Debt Instrument [Line Items]
Total Outstanding			$ 1,185,000,000				$ 1,185,000