Derivatives (Narrative) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments [Line Items]
Estimate increase to interest expense	$ 4,900
Derivative, notional amount	$ 1,047,300
Derivative, Maturity Date	May 23, 2023
Repayment of mortgage loans	$ 0	$ 150,000	$ 280,327
Lycoming Mall [Member]
Derivative Instruments [Line Items]
Loss recognized in income on derivatives (ineffective portion and amount excluded from effectiveness testing)		$ (100)
Interest rate swap [Member]
Derivative Instruments [Line Items]
Derivative, Weighted average interest rate	1.55%
Derivative, notional amount	$ 797,300
Interest Rate Swap Member Forward Starting [Member]
Derivative Instruments [Line Items]
Derivative, Weighted average interest rate	2.71%
Derivative, notional amount	$ 250,000