Real Estate and Accumulated Depreciation (Notes to Schedule III) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Real Estate
Balance at beginning of period	$ 3,893,799	$ 3,814,986	$ 2,606,343
Additions during the period:
Acquisitions	48,920	62,723	0
Improvements and other capitalized costs	178,567	303,940	208,016
Transfers	0	0	5,306
Total Additions	227,487	366,663	3,046,052
Deductions during the period:
Parkway spin-off	0	0	(1,230,235)
Cost of real estate sold	0	(287,850)	(602,648)
Impairment loss	0	0	(4,526)
Total Deductions	0	(287,850)	(1,837,409)
Balance at end of period	4,121,286	3,893,799	3,814,986
Accumulated Depreciation
Balance at beginning of period	275,977	215,856	359,422
Additions during the period:
Acquisitions	0	0	0
Improvements and other capitalized costs	0	0	0
Transfers	0	0	0
Depreciation expense	145,518	101,720	112,277
Total Additions	145,518	101,720	112,277
Deductions during the period:
Parkway spin-off	0	0	(148,523)
Cost of real estate sold	0	(41,599)	(107,320)
Impairment loss	0	0	0
Total Deductions	0	(41,599)	(255,843)
Balance at end of period	421,495	275,977	215,856
Aggregate cost for federal income tax, net of depreciation	$ 3,000,000
Buildings and Improvements | Minimum
Deductions during the period:
Useful life	30 years
Buildings and Improvements | Maximum
Deductions during the period:
Useful life	42 years
Parkway merger
Additions during the period:
Acquisitions	$ 0	0	2,832,730
Additions during the period:
Acquisitions	$ 0	$ 0	$ 0