New Accounting Pronouncements Leases (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Leases [Abstract]
Expense impact of costs attributable to successful leasing activities	$ 1,123,000	$ 0	$ 6,726,000	$ 0
Increase (Decrease) in Deferred Leasing Fees		$ 852,000		$ 9,200,000
Rental revenue - fixed payments	163,516,000		481,674,000
Rental revenue - variable payments (1)	51,858,000		156,772,000
Rental and related revenue	215,374,000		638,446,000
2019	153,301,000		153,301,000		$ 600,385,000
2020	623,291,000		623,291,000		586,609,000
2021	600,850,000		600,850,000		529,961,000
2022	537,556,000		537,556,000		463,462,000
2023	466,514,000		466,514,000		397,150,000
Thereafter	2,058,372,000		2,058,372,000		1,582,598,000
Lessor, Operating Lease, Payments to be Received	4,439,884,000		4,439,884,000		4,160,165,000
Operating Lease, Right-of-Use Asset	38,800,000		38,800,000
Operating Lease, Liability	45,021,000		45,021,000
2019	1,521,000		1,521,000		6,487,000
2020	8,037,000		8,037,000		7,594,000
2021	3,595,000		3,595,000		2,987,000
2022	2,877,000		2,877,000		2,255,000
2023	2,585,000		2,585,000		1,949,000
Thereafter	86,040,000		86,040,000		85,523,000
Total undiscounted operating lease payments	104,655,000		104,655,000		$ 106,795,000
Less: imputed interest	$ (59,634,000)		$ (59,634,000)
Operating Lease, Weighted Average Remaining Lease Term	32 years 6 months		32 years 6 months
Operating Lease, Weighted Average Discount Rate, Percent	4.55%		4.55%