EQUITY - Narrative (Details)				6 Months Ended		10 Months Ended	12 Months Ended
	Mar. 20, 2018 USD ($) $ / shares shares	May 15, 2017 USD ($)	May 09, 2017 $ / shares shares	Jun. 30, 2018 USD ($) $ / shares shares	Jun. 30, 2017 USD ($) shares	May 25, 2017 USD ($) $ / shares shares	Dec. 31, 2017 $ / shares shares
Class of Stock [Line Items]
Common stock, shares authorized | shares				500,000,000			500,000,000
Common stock, par value (in dollars per share)				$ 0.01			$ 0.01
Shares issued during stock offering (in shares) | shares				0	10,350,000
Net proceeds from public shares offering | $					$ 163,670,000
Payments of stock issuance costs | $				$ 100,000
Compensation entitled as percentage of gross proceeds of shares sold under sales agreements				2.00%
Preferred stock, shares authorized | shares				100,000,000			100,000,000
Preferred stock, par value (in dollars per share)				$ 0.01			$ 0.01
Undesignated preferred stock
Class of Stock [Line Items]
Preferred stock, shares authorized | shares				90,600,000
9.25% Series A Preferred Stock
Class of Stock [Line Items]
Preferred stock, liquidation preference (in dollars per share)				$ 25
7.875% Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock, liquidation preference (in dollars per share)				25
7.125% Series C Preferred Stock
Class of Stock [Line Items]
Preferred stock, dividend rate							7.125%
Payments for repurchase of redeemable preferred shares | $	$ 85,300,000
Preferred stock, shares outstanding | shares	3,400,000						3,400,000
Preferred stock, redemption price (in dollars per share)	$ 25
Preferred stock, liquidation preference (in dollars per share)				$ 25
6.45% Series D Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized | shares				3,000,000
Preferred stock, dividend rate				6.45%			6.45%
Preferred stock, shares outstanding | shares				3,000,000			3,000,000
Preferred stock, liquidation preference (in dollars per share)				$ 25
Annual dividend rate per share (in dollars per share)				$ 1.6125
6.45% Series D Preferred Stock | Maximum
Class of Stock [Line Items]
Ratio for conversion				3.9216
6.25% Series E Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized | shares				6,400,000
Preferred stock, dividend rate				6.25%			6.25%
Preferred stock, shares outstanding | shares				6,400,000			6,400,000
Preferred stock, liquidation preference (in dollars per share)				$ 25
Annual dividend rate per share (in dollars per share)				$ 1.5625
6.25% Series E Preferred Stock | Maximum
Class of Stock [Line Items]
Ratio for conversion				3.1686
Operating partnership | Non-controlling Interests in Operating Partnership
Class of Stock [Line Items]
Number of common units of operating partnership owned by unaffiliated third parties (in shares) | shares				297,552			323,391
Percentage of limited partnership interest in operating partnership (less than)				1.00%			1.00%
Underwriting Agreement
Class of Stock [Line Items]
Common stock, par value (in dollars per share)			$ 0.01
Shares issued during stock offering (in shares) | shares			9,000,000
Public offering price (in dollars per share)			$ 16.50
Underwriting discount (in dollars per share)			$ 0.66
Number of days option for underwriters to purchase common stock on same terms			30 days
Number of additional shares for underwriters to purchase | shares			1,350,000
Net proceeds from public shares offering | $		$ 163,800,000
Underwriting discount and offering-related expenses | $		$ 7,000,000
2017 ATM Program
Class of Stock [Line Items]
Common stock, par value (in dollars per share)						$ 0.01
Common stock, shares authorized, amount | $						$ 200,000,000
2016 ATM Program
Class of Stock [Line Items]
Shares issued during stock offering (in shares) | shares						6,151,514
Net proceeds from public shares offering | $						$ 89,100,000
Unaffiliated Third Parties | Operating partnership
Class of Stock [Line Items]
Limited partner capital account units conversion ratio				1