Financing Activity - Mortgage Loan Activity Additional Detail (Detail) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Mortgage Loan Activity [Line Items]
Mortgage loans payable, net	$ 1,056,686	$ 1,056,084
Common Stock, Dividends, Per Share, Cash Paid	$ 0.42
Maximum Unsecured Borrowing Amount Under Unencumbered Debt Yield Covenant	$ 239,600
Carrying Value Of Net Losses Associated With Interest Rate Swaps	200
Derivative, Notional Amount	1,048,200
Two Thousand Thirteen Revolving Credit Facility [Member]
Mortgage Loan Activity [Line Items]
Letters of Credit Outstanding, Amount	14,800
Wyoming Valley Mall [Member]
Mortgage Loan Activity [Line Items]
Mortgage loans payable, net	74,400
Secured Debt [Member]
Mortgage Loan Activity [Line Items]
Debt Issuance Costs, Line of Credit Arrangements, Net	$ 3,500	$ 3,400