Real Estate Investments - Discontinued Operations and Assets Held for Sale - Balance Sheet (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Balance Sheet data (as of the period ended):
Land	$ 230,206	$ 230,206
Investment Building and Building Improvements	3,757,260	3,675,415
Real estate properties, Total	4,063,178	3,974,071
Accumulated depreciation	(1,035,800)	(1,015,174)
Total real estate properties, net	3,027,378	2,958,897
Liabilities of properties held for sale	633	587
Inpatient Rehabilitation Facility | Disposal Group, Held-for-sale, Not Discontinued Operations
Balance Sheet data (as of the period ended):
Land	1,125	1,125
Investment Building and Building Improvements	39,586	18,231
Real estate properties, Total	40,711	19,356
Accumulated depreciation	(30,706)	(10,657)
Total real estate properties, net	10,005	8,699
Operating lease right-of-use assets	168	0
Other assets, net	395	573
Assets held for sale, net	10,568	9,272
Accounts payable and accrued liabilities	251	450
Operating lease liabilities	168	0
Other liabilities	214	137
Liabilities of properties held for sale	$ 633	$ 587