Revenue Recognition (Components of Lease Revenue) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Fixed billings	$ 1,292,174	$ 1,531,917
Variable billings	126,907	199,291
Total contractual operating lease billings	1,419,081	1,731,208
Adjustment for straight-line rents and amortization of acquired below-market leases, net	(12,486)	5,739
Less: write-off of straight-line rent and tenant receivables deemed uncollectible	(63,204)	(17,237)	$ 0
Lease revenues	$ 1,343,391	$ 1,719,710