New Accounting Pronouncements Leases (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Leases [Abstract]
Expense impact of costs attributable to successful leasing activities	$ (3,447)	$ 0	$ (5,603)	$ 0
Increase (Decrease) in Deferred Leasing Fees		$ 2,600		$ 7,200
Rental revenue - fixed payments	161,483		318,157
Rental revenue - variable payments (1)	51,624		104,915
Rental and related revenue	213,107		423,072
2019	312,844		312,844		$ 600,385
2020	624,674		624,674		586,609
2021	587,383		587,383		529,961
2022	521,164		521,164		463,462
2023	450,616		450,616		397,150
Thereafter	1,999,848		1,999,848		1,582,598
Lessor, Operating Lease, Payments to be Received	4,496,529		4,496,529		4,160,165
Operating Lease, Right-of-Use Asset	37,800		37,800
Operating Lease, Liability	43,695		43,695
2019	2,990		2,990		6,487
2020	7,673		7,673		7,594
2021	3,069		3,069		2,987
2022	2,339		2,339		2,255
2023	2,034		2,034		1,949
Thereafter	85,559		85,559		85,523
Total undiscounted operating lease payments	103,664		103,664		$ 106,795
Less: imputed interest	$ (59,969)		$ (59,969)
Operating Lease, Weighted Average Remaining Lease Term	33 years 4 months 24 days		33 years 4 months 24 days
Operating Lease, Weighted Average Discount Rate, Percent	4.61%		4.61%