SUBSEQUENT EVENTS (Details)		9 Months Ended	12 Months Ended
	Oct. 30, 2017 $ / shares	Sep. 30, 2017	Dec. 31, 2016	Oct. 27, 2017 USD ($)	Oct. 02, 2017 USD ($) Instrument
7.875% Series B Preferred Stock
Subsequent events
Preferred stock, dividend rate		7.875%	7.875%
7.125% Series C Preferred Stock
Subsequent events
Preferred stock, dividend rate		7.125%	7.125%
6.450% Series D Preferred Stock
Subsequent events
Preferred stock, dividend rate		6.45%	6.45%
Subsequent Event
Subsequent events
Cash dividends declared, common stock (in dollars per share)	$ 0.17
Subsequent Event | 7.875% Series B Preferred Stock
Subsequent events
Cash dividends declared, preferred stock (in dollars per share)	0.4921875
Subsequent Event | 7.125% Series C Preferred Stock
Subsequent events
Cash dividends declared, preferred stock (in dollars per share)	0.4453125
Subsequent Event | 6.450% Series D Preferred Stock
Subsequent events
Cash dividends declared, preferred stock (in dollars per share)	$ 0.403125
Interest rate swaps | Subsequent Event
Subsequent events
Number of derivative agreements entered | Instrument					2
Derivative notional amount | $					$ 100,000,000
Derivative average fixed interest rate					1.98%
Mezzanine Loans | Subsequent Event
Subsequent events
Net amount of loan receivable | $				$ 12,000,000
Funded amount of loan receivable | $				$ 7,200,000
Interest in hotel upon completion to purchase				90.00%