SCHEDULE III - REAL ESTATE AND ACCUMULATED DEPRECIATION - Property Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Real Estate Assets
Balance, beginning of period	$ 1,228,780	$ 2,021,494	$ 2,061,372
Additions
Improvements	14,906	26,078	31,844
Property acquisitions	128,928	18,770	0
Deductions:
Assets held for sale	(24,832)	0	0
Asset sales	0	(815,357)	(61,801)
Impairment	0	(13,100)	0
Retirements	(3,146)	(9,105)	(9,921)
Balance, end of period	1,344,636	1,228,780	2,021,494
Accumulated Depreciation
Balance, beginning of period	(271,055)	(414,552)	(369,661)
Additions: Depreciation	(43,499)	(49,427)	(62,239)
Assets held for sale	7,709	0	0
Asset sales	0	183,819	7,427
Deductions: retirements	3,146	9,105	9,921
Balance, end of period	$ (303,699)	$ (271,055)	$ (414,552)