INCOME TAXES - Tax Rate Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effective Income Tax Rate Reconciliation, Percent [Abstract]
US statutory tax rate		35.00%	35.00%	35.00%
REIT income not subject to corporate income tax		(29.53%)	(34.38%)	(32.37%)
Increase due to state and local taxes		0.74%	4.41%	1.40%
Deferred tax asset write-off upon conversion to REIT		0.00%	0.00%	1.44%
Change in valuation allowance		2.13%	0.42%	3.29%
Impact of Tax Cuts and Jobs Act		(2.53%)	0.00%	0.00%
Other		(0.04%)	(0.19%)	0.39%
Effective income tax rate		5.77%	5.26%	9.15%
State and Local Jurisdiction \| New York
Effective Income Tax Rate Reconciliation, Percent [Abstract]
State income tax expense (benefit)	$ 3.3		$ 3.3

Effective Income Tax Rate Reconciliation, Deferred Tax Assets Written Off, Percent

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Effective Income Tax Rate Reconciliation, Tax Cuts And Jobs Act Of 2017, Percent

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 13
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-Name Accounting Standards Codification
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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to changes in the valuation allowance for deferred tax assets.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

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