Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Minimum Future Rental Receipts [Abstract]
2019	$ 270,557
2020	253,660
2021	233,192
2022	212,893
2023	211,387
Thereafter	1,619,848
Future Minimum Payments Receivable	2,801,537
Leaseholds Interests [Member]
Future Rental Payments [Abstract]
2019	3,826
2020	3,827
2021	3,769
2022	3,834
2023	4,008
Thereafter	28,326
Future Minimum Payments Due	47,590
Rent expense for leasehold interests	597	$ 690	$ 987
Corporate HQ and Office Space [Member]
Future Rental Payments [Abstract]
2019	1,295
2020	1,296
2021	1,325
2022	1,335
2023	1,304
Thereafter	2,935
Rent expense for leasehold interests	$ 1,274	$ 1,256	$ 1,242