Leases ASC 840 (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating leases, scheduled future minimum payments receivable [Abstract]
2019	$ 618,014
2020	581,399
2021	524,381
2022	488,157
2023	428,461
Thereafter	2,068,891
Operating leases, total future minimum payments receivable due	4,709,303
Leases, Operating [Abstract]
Total rental property expense recorded for operating ground leases	2,500	$ 2,500	$ 2,900
Operating ground leases, scheduled future minimum payments [Abstract]
2019	2,184
2020	2,223
2021	2,263
2022	2,305
2023	2,308
Thereafter	86,577
Operating ground leases, total future minimum payments due	$ 97,860