Leases (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) property	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jan. 01, 2019 USD ($)
Operating Leased Assets [Line Items]
Fixed and in-substance fixed lease income	$ 807,603	$ 813,444
Variable lease income	247,384	247,861
Uncollectible straight line rent	(34,673)	(7,002)
Uncollectible amounts billable in lease income	(82,367)	(5,394)
Total lease income	980,166	1,094,301	$ 1,083,770
2021	754,396
2022	676,083
2023	578,023
2024	480,768
2025	372,377
Thereafter	1,329,274
Total	$ 4,190,921
Number of Properties Subject to Ground Leases | property	22
Last Ground Lease Expiration Date	2101
Last Office Lease Expiration Date	2029
Operating Lease, Expense	$ 19,679	20,456	$ 19,100
Variable Lease, Cost	1,629	2,245
Operating cash flows for operating leases	15,003	14,815
Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months	15,432
Lessee, Operating Lease, Liability, Payments, Due Year Two	14,216
Lessee, Operating Lease, Liability, Payments, Due Year Three	13,634
Lessee, Operating Lease, Liability, Payments, Due Year Four	13,217
Lessee, Operating Lease, Liability, Payments, Due Year Five	13,067
Lessee, Operating Lease, Liability, Payments, Due after Year Five	544,961
Lessee, Operating Lease, Total Undiscounted Lease Liabilities	614,527
Lessee, Operating Lease, Present Value Discount	(394,137)
Lease liabilities	220,390	222,918		$ 225,400
Lessor [Member]
Operating Leased Assets [Line Items]
Above/below market rent and tenant rent inducement amortization, net	42,219	45,392
Ground Lease [Member]
Operating Leased Assets [Line Items]
Operating Lease, Expense	13,716	13,982
Variable Lease, Cost	1,044	1,693
Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months	10,778
Lessee, Operating Lease, Liability, Payments, Due Year Two	10,837
Lessee, Operating Lease, Liability, Payments, Due Year Three	11,054
Lessee, Operating Lease, Liability, Payments, Due Year Four	11,103
Lessee, Operating Lease, Liability, Payments, Due Year Five	11,106
Lessee, Operating Lease, Liability, Payments, Due after Year Five	542,184
Lessee, Operating Lease, Total Undiscounted Lease Liabilities	597,062
Lessee, Operating Lease, Present Value Discount	(392,848)
Lease liabilities	$ 204,214
Operating Lease, Weighted Average Discount Rate, Percent	5.20%
Operating Lease, Weighted Average Remaining Lease Term	48 years 1 month 6 days
Office Lease [Member]
Operating Leased Assets [Line Items]
Operating Lease, Expense	$ 4,334	4,229
Variable Lease, Cost	585	552
Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months	4,654
Lessee, Operating Lease, Liability, Payments, Due Year Two	3,379
Lessee, Operating Lease, Liability, Payments, Due Year Three	2,580
Lessee, Operating Lease, Liability, Payments, Due Year Four	2,114
Lessee, Operating Lease, Liability, Payments, Due Year Five	1,961
Lessee, Operating Lease, Liability, Payments, Due after Year Five	2,777
Lessee, Operating Lease, Total Undiscounted Lease Liabilities	17,465
Lessee, Operating Lease, Present Value Discount	(1,289)
Lease liabilities	$ 16,176
Operating Lease, Weighted Average Discount Rate, Percent	3.80%
Operating Lease, Weighted Average Remaining Lease Term	5 years
Fixed Lease Expense [Member]
Operating Leased Assets [Line Items]
Operating Lease, Expense	$ 18,050	$ 18,211