Leases ASC 840 (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Allowance For Doubtful Accounts [Roll Forward]
Allowance for doubtful accounts, beginning balance	$ 1,644	$ 1,421
Additions to allowance for doubtful accounts	1,568	2,003
Deductions to allowance for doubtful accounts	(1,361)	(1,780)
Allowance for doubtful accounts, ending balance	1,851	1,644
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
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
Allowance for Doubtful Accounts - Straight Line Rent [Member]
Allowance For Doubtful Accounts [Roll Forward]
Allowance for doubtful accounts, beginning balance	819	692
Additions to allowance for doubtful accounts	599	1,503
Deductions to allowance for doubtful accounts	(777)	(1,376)
Allowance for doubtful accounts, ending balance	641	819
Allowance for Doubtful Accounts - Accounts Receivable [Member]
Allowance For Doubtful Accounts [Roll Forward]
Allowance for doubtful accounts, beginning balance	753	624
Additions to allowance for doubtful accounts	969	500
Deductions to allowance for doubtful accounts	(556)	(371)
Allowance for doubtful accounts, ending balance	1,166	753
Allowance for Doubtful Accounts - Notes Receivable [Member]
Allowance For Doubtful Accounts [Roll Forward]
Allowance for doubtful accounts, beginning balance	72	105
Additions to allowance for doubtful accounts	0	0
Deductions to allowance for doubtful accounts	(28)	(33)
Allowance for doubtful accounts, ending balance	$ 44	$ 72