ACQUISITIONS AND DISPOSITIONS - Disposals (Details) $ in Thousands			3 Months Ended		6 Months Ended
	Mar. 28, 2017 USD ($) ft²	Feb. 02, 2016 USD ($) room	Mar. 31, 2017 USD ($) property agreement business	Mar. 31, 2016 USD ($) business	Sep. 30, 2017 USD ($)
Disposals
Number of business acquisitions | business			0	0
Sales price			$ 289,939	$ 42,782
Gain on sale of real estate			$ 187,734	24,739
Liabilities
Number of purchase and sales agreements entered into | agreement			5
Payment of mortgages payable			$ 26,477	$ 1,068
211 Main Street, San Francisco | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Disposals
Ownership sold, percentage	100.00%
Sale transaction costs	$ 2,943
Mortgage prepayment penalty	$ 1,508
Property area | ft²	417,266
Sales price	$ 292,882
Gain on sale of real estate	187,734
Assets
Investments in real estate, net	93,747
Deferred rent receivable and charges, net	10,822
Other intangible assets, net	32
Total assets	104,601
Liabilities
Debt, net	25,996
Intangible liabilities, net	1,731
Total liabilities	27,727
Premium on assumed mortgage	$ 665
Courtyard Oakland located in Oakland California | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Disposals
Ownership sold, percentage		100.00%
Number of rooms | room		162
Sales price		$ 43,800
Gain on sale of real estate		$ 24,739
3636 McKinney Avenue and 3839 McKinney Avenue, Dallas, Texas
Liabilities
Number of real estate properties | property			2
Scenario, Forecast
Liabilities
Payment of mortgages payable					$ 60,600
Scenario, Forecast | 200 S College Street, 980 9th Street, 1010 8th Street, 7083 Hollywood Boulevard, 4649 Cole Avenue, 3636 McKinney Avenue, 3839 McKinney Avenue
Disposals
Sales price					$ 409,400