Leases Lessee (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) property	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jan. 01, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Ground and Operating Lease Obligation Due	$ 699,900			$ 590,300
Operating lease liability	271,808	$ 0		218,700
Operating lease right-of-use asset	$ 264,709	0
Operating lease discount rate	5.24%
Number of Properties Subject to Ground Leases | property	31
Net book value for the exclusion of one ground lease related to one operating property	$ 7,700
Operating Lease Obligation Remaining Lease Term	15 years
Operating lease costs - cash rents	$ 17,700	14,800	$ 14,600
Operating Lease Liabilities, Payment Due
2020	15,132
2021	15,931
2022	16,467
2023	16,628
2024	16,857
Thereafter	618,924
Total future payments under our operating leases in which we are the lessee	699,939
Effect of discounting	(428,131)
Operating lease liability	271,808	0		$ 218,700
Lessee operating costs
Gross operating lease costs	19,740	16,102	14,307
Capitalized lease costs	(1,452)	(340)	(340)
Expenses for operating leases in which we are lessee	$ 18,288	$ 15,762	$ 13,967
Minimum
Lessee, Lease, Description [Line Items]
Remaining lease term for ground lease obligation	34 years
Maximum
Lessee, Lease, Description [Line Items]
Remaining lease term for ground lease obligation	95 years
Ground and Operating Leases
Lessee, Lease, Description [Line Items]
Weighted average remaining lease term	44 years