Summary of Significant Accounting Policies Leasing (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Recently Adopted New Accounting Pronouncement (Leases) [Abstract]
Expense impact of costs attributable to successful leasing activities	$ 12,402	$ 0	$ 0
Increase (Decrease) in Deferred Leasing Fees		12,300
Operating Lease, Lease Income, Lease Payments	645,759	587,187	585,064
Operating Lease, Variable Lease Income	210,074	198,249	188,635
Operating Lease, Lease Income	855,833	785,436	$ 773,699
2020	641,578
2021	640,615
2022	577,591
2023	507,101
2024	439,324
Thereafter	1,954,723
Lessor, Operating Lease, Payments to be Received	4,760,932
Operating Lease, Right-of-Use Asset	40,500
Operating Lease, Liability	46,902
2020	8,299	6,487
2021	3,864	7,594
2022	3,655	2,987
2023	3,431	2,255
2024	2,865	1,949
Thereafter	84,119	85,523
Total undiscounted operating lease payments	106,233	$ 106,795
Less: imputed interest	$ 59,331
Operating Lease, Weighted Average Remaining Lease Term	31 years 4 months 24 days
Operating Lease, Weighted Average Discount Rate, Percent	4.47%