Discontinued Operations (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rental revenue	$ 135,043	$ 140,292
Interest and Fee Income, Loans, Commercial and Residential, Real Estate	8,396	9,891
Revenues	151,012	150,527
Property operating expense	13,093	15,551
Interest expense, net	(34,753)	(33,963)
Depreciation and amortization	43,810	36,002
Income from discontinued operations before other items	0	10,169
Gain (Loss) on Disposition of Real Estate, Discontinued Operations	0	6,716
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0	16,885
Proceeds from Sale of Real Estate	2,907	37,810
Payments to Acquire Mortgage Notes Receivable	(2,002)	(10,998)
Proceeds from Sale and Collection of Mortgage Notes Receivable	94	973
Payments to Develop Real Estate Assets	(16,118)	(61,910)
Interest cost capitalized	$ 262	3,137
Public Charter School Portfolio Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
number of properties sold			47
Proceeds from Sale of Property, Plant, and Equipment			$ 449,600
Discontinued Operations, Disposed of by Sale [Member] | Public Charter School Portfolio Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rental revenue		10,431
Interest and Fee Income, Loans, Commercial and Residential, Real Estate		3,584
Revenues		14,015
Property operating expense		242
Interest expense, net		(137)
Depreciation and amortization		3,741
Income from discontinued operations before other items		10,169
Gain (Loss) on Disposition of Real Estate, Discontinued Operations		6,716
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent		16,885
Payments to Acquire Productive Assets		(1,573)
Proceeds from Sale of Real Estate		28,004
Payments to Acquire Mortgage Notes Receivable		(3,280)
Proceeds from Sale and Collection of Mortgage Notes Receivable		889
Payments to Develop Real Estate Assets		(5,790)
Real Estate Owned, Transfer from Real Estate Owned		48
Interest cost capitalized		$ 137