Schedule III - Schedule of Real Estate and Accumulated Depreciation (Reconciliation of Real Estate Accumulated Depreciation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule III - Schedule of Real Estate and Accumulated Depreciation [Abstract]
Gross amount of accumulated depreciation at beginning	$ (2,868,507)	$ (2,627,841)	$ (2,396,587)
Depreciation	(269,606)	(257,469)	(248,818)
Other	(83)	(25)
Total additions	(269,689)	(257,494)	(248,818)
Amount of accumulated depreciation for assets sold or disposed	2,887	4,392	17,051
Other	2,248	12,436	513
Total deductions	5,135	16,828	17,564
Balance at end	$ (3,133,061)	$ (2,868,507)	$ (2,627,841)