New Accounting Pronouncements Leases (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Leases [Abstract]
Rental revenue - fixed payments	$ 156,674
Rental revenue - variable payments (1)	53,291
Rental and related revenue	209,965
Expense impact of costs attributable to successful leasing activities	(2,156)	$ 0
2019	463,579		$ 600,385
2020	604,917		586,609
2021	548,979		529,961
2022	480,747		463,462
2023	411,773		397,150
Thereafter	1,637,200		1,582,598
Lessor, Operating Lease, Payments to be Received	4,147,195		4,160,165
Operating Lease, Right-of-Use Asset	38,800
Operating Lease, Liability	44,472
2019	4,618		6,487
2020	7,594		7,594
2021	2,987		2,987
2022	2,255		2,255
2023	1,949		1,949
Thereafter	85,523		85,523
Total undiscounted operating lease payments	104,926		$ 106,795
Less: imputed interest	$ (60,454)
Operating Lease, Weighted Average Remaining Lease Term	32 years 10 months 24 days
Operating Lease, Weighted Average Discount Rate, Percent	4.62%
Increase (Decrease) in Deferred Leasing Fees		$ 4,700