DISCONTINUED OPERATIONS - Effect on Net Income and Gains (Losses) From Sale Of Property (Details) $ in Thousands	2 Months Ended	3 Months Ended										8 Months Ended		12 Months Ended
	Dec. 31, 2018 USD ($)	Oct. 31, 2018 USD ($)	Jul. 31, 2018 USD ($)	Apr. 30, 2018 USD ($)	Jan. 31, 2018 USD ($)	Oct. 31, 2017 USD ($)	Jul. 31, 2017 USD ($)	Apr. 30, 2017 USD ($)	Jan. 31, 2017 USD ($)	Oct. 31, 2016 USD ($)	Jul. 31, 2016 USD ($)	Dec. 31, 2018 USD ($) property	Dec. 31, 2017 USD ($)	Apr. 30, 2018 USD ($) property	Apr. 30, 2017 USD ($) property	Apr. 30, 2016 USD ($) property
Revenues [Abstract]
Real estate rentals												$ 117,575
Revenues	$ 30,287	$ 45,638	$ 45,946	$ 44,185	$ 42,716	$ 41,866	$ 40,978	$ 42,811	$ 39,797	$ 39,195	$ 38,301	121,871	$ 111,249	$ 169,745	$ 160,104	$ 145,500
EXPENSES
Property operating expenses, excluding real estate taxes												37,198	35,581	54,292	47,587	43,741
Real estate taxes												13,521	12,234	18,742	16,739	14,407
Depreciation and amortization												50,456	54,902	82,070	44,253	39,273
Impairment of real estate investments												1,221		18,065	57,028	5,543
TOTAL EXPENSES												116,786	116,266	193,449	190,214	121,244
Interest expense												(21,359)	(22,804)	(34,178)	(34,314)	(28,417)
Gain (loss) on extinguishment of debt												(556)	(818)	(940)	(1,651)	(106)
Interest income												1,168	432	1,197	366	78
Other income												65	282	311	780	307
Gain (loss) on sale of discontinued operations												10,277		183,687	74,847	33,423
INCOME FROM DISCONTINUED OPERATIONS												570	150,703	164,823	76,753	67,420
Property Sale Data
Gain (loss) on sale of discontinued operations												$ 10,277		$ 183,687	$ 74,847	33,423
Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of real estate properties classified as discontinued operations | property												0		27	0
EXPENSES
Gain (loss) on sale of discontinued operations												$ 0		$ 163,567	$ 56,146	23,782
Default interest																4,700
Non-recourse loan																122,600
Gain on extinguishment of debt from transfer of ownership																$ 36,500
Number of loan properties | property																9
Property Sale Data
Sales price												0		437,652	239,436	$ 373,460
Net book value and sales costs												0		(274,085)	(183,290)	(349,678)
Gain (loss) on sale of discontinued operations												0		163,567	56,146	23,782
Discontinued Operations, Disposed of by Sale
Revenues [Abstract]
Real estate rentals												0		19,744	43,984	69,623
EXPENSES
Property operating expenses, excluding real estate taxes												0		6,350	9,051	17,470
Real estate taxes												0		5,191	6,848	11,611
Depreciation and amortization												0		8,445	10,772	24,725
Impairment of real estate investments												0		0	0	440
TRS senior housing expenses												0		0	3,113	3,366
TOTAL EXPENSES												0		20,192	30,358	59,569
Operating income (loss)												0		11,202	32,954	37,443
Interest expense												0		(4,172)	(11,628)	(25,757)
Gain (loss) on extinguishment of debt												0		(6,508)	(3,238)	29,336
Interest income												0		661	2,179	2,179
Other income												0		73	340	437
Income (loss) from discontinued operations before gain on sale												0		1,256	20,607	43,638
Gain (loss) on sale of discontinued operations												570		163,567	56,146	23,782
INCOME FROM DISCONTINUED OPERATIONS												570		164,823	76,753	67,420
Property Sale Data
Gain (loss) on sale of discontinued operations												570		163,567	$ 56,146	$ 23,782
Discontinued Operations, Disposed of by Sale | Office
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of real estate properties classified as discontinued operations | property																48
Discontinued Operations, Disposed of by Sale | Retail Site
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of real estate properties classified as discontinued operations | property																17
Discontinued Operations, Disposed of by Sale | Commercial Healthcare
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of real estate properties classified as discontinued operations | property																1
Discontinued Operations, Disposed of by Sale | Senior Housing Properties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of real estate properties disposed | property															32
Discontinued Operations, Disposed of by Sale | All Other
EXPENSES
INCOME FROM DISCONTINUED OPERATIONS												570		164,823	$ 76,753	$ 67,420
Discontinued Operations, Held-for-sale | Senior Housing Properties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties classified as held for sale | property																34
Tenant Reimbursement | Discontinued Operations, Disposed of by Sale
Revenues [Abstract]
Revenues												0		11,650	16,110	$ 23,434
TRS Senior Housing | Discontinued Operations, Disposed of by Sale
Revenues [Abstract]
Revenues												0		0	3,218	3,955
Real Estate
EXPENSES
Property management expense												50,719		73,034	64,326	58,148
Real Estate | Discontinued Operations, Disposed of by Sale
Revenues [Abstract]
Revenues												0		31,394	63,312	97,012
Management Service
EXPENSES
Property management expense												3,663	$ 3,652	5,526	5,046	3,714
Management Service | Discontinued Operations, Disposed of by Sale
EXPENSES
Property management expense												$ 0		$ 206	$ 574	$ 1,957